Well, how low can you go? 10k? 8k? Surely 6-8k at least for a decent sounding set up? Nope, turns out thats too much. Read on.
The Background
So I got the Chevy spark handed down to me by my sister who moved abroad. I don't have a lot of use for a car currently, but i may need it for a couple of months in my upcoming postings in my Internship. With it being a 2011 model and having developed some major clutch issues in the last couple of years, my dad isn't too intent on keeping it around for long. (He was ready to sell it off, heck even put an online ad before i told him I may need the car occasionally ). I being so attached to the car (had a lot of firsts in it ), with all my begging finally got him to keep it till at least the end of the year.
I had gotten all the mechanical issues sorted out a few months ago so I didn't see any problem with it. A few times i went out with friends and played some music on it, i Immediately saw a problem, the ICE. While it did have a decent blaupunkt HU, I was running a rear tray speaker setup only with an Old pioneer set that I got from the giveaway thread. Originally I did have the front dash speakers as well but they were shot shortly before I got the time to install the rear speakers and with the better bass output of the bigger speakers, I wasn't complaining. As time went on, the backlight of the Blaupunkt HU gave way, and I also noticed the bass of the pioneers also went down. I had issues with the AUX port on the HU and I was limited to Radio or USB to get a decent sound. Something had to be done.
The Plan
Given that I knew i wouldn't be keeping the car for a long period of time, new parts were out of the picture. Simple reason: Any car i buy next year won't necessarily have the space for a new HU or the now nearly obsolete 4 inch and 6x9 speakers.
Thus, I was looking into used options. I was thinking of getting better speakers first and then if possible getting an HU with bluetooth for the added convenience. I went to a couple of guys selling their old tray speakers on OLX but as it turned out my current speakers sounded better

New 6x9 from Sony/pioneer cost about 2.5k, so I was happy to pay about half of that if possible.
Saw a video on youtube about installing a 20$ HU from a walmart and that guy was able to drive basic Sony 6" speakers from it and they sounded better than a stock setup. Looked around for a similar option in India and I could only find chinese HUs that cost about 1800-2k online, and the 6x9 speakers weren't much cheaper close to 1500 for a pair. I thought better to go for branded ones than to experiment with such things.
Then I stumbled on to a video showing the dirt cheap Car audio options at Kashmere gate, the same HU i saw online was half the price! Then, one day when I got frustrated with another guy from OLX trying to pass broken speakers, drove straight to kashmere gate.
The HAUL
Went to a few shops and it was clear everybody had the same chinese/local stuff that was available online but for half the price here. Bought a Bluetooth HU and a set of front speakers from one shop. and then bought a pair of 6x9 speakers from another shop for a mouth wateringly low price.
Went to the Karol bagh, "radio lane" to get the stuff installed since I didn't have the required coupler to get the wiring harness installed correctly. Had a few accessories installed along like a new antenna and a white led interior light. After the install I was happy to get a good sound that finally had some bass in it. But it had an issue where sometimes the HU would refuse to turn on without cycling the car on and off, and it had no memory i.e. the clock and presets would be reset. Finally swapped the red and yellow wires and that was fixed. I was happy with it for a couple of weeks and was frankly surprised at the level of clarity and features that the system offered. Bluetooth was working flawlessly and connecting to my phone everytime I turned it on. Then one day, while playing around with the settings, I found that i was getting better bass if i played the sound off center. Looked online and team bhp helped me to diagnose that my speakers were wired out of phase. changed my wires around and put in proper crimp connectors and DANG!
Turned on the loud mode on the HU and the amount of bass from the rear speakers was Fantastic. The treble with the help of the smaller dash speakers was already pretty good and this completed the package. It sounds as goood as a basic Brand name setup that would cost around 10k. About 6k for the HU , 2.5 and 1.5 for the rear and front speakers respectively.
The COST
Head unit : 900
Front speakers: 450
Rear speakers: 750
Total : 2100
Yes, that's right my setup cost about fifth of the price of what i could find from something like Sony/Pioneer. And with a BT headunit i don't see any usability issues with it and I am very satisfied with the sound out of it.
Disclaimer
I know that this is not the kind of thread that comes around on the ICE section of the forum because most of us aren't this miser when giving our cars some TLC and ICE. I know that some of us are audiophiles and want a much better sounding and a more reliable setup than what I told about. I have a thing for audio too, I have headphones that increase the value of my spark a third when put in it but i didn't see the point in spending big money on what is frankly a beater car that i won't be keeping with me for much longer. I was skeptical about the kind of sound I would get out of such a cheap setup but I was positively surprised. So if you too have a car that has an ICE on its last legs or if you are sick of your beater car not having Bluetooth, just get this new HU
Smaller yet significant thing
The software on this HU is complete trash, it can't even display the name of the song it is streaming on BT, heck it can't even keep the clock on it for more than 5 seconds before reverting back to the Source type on its screen. But it does have a very useful feature that i don't see with most aftermarket players. You know when you turn your car from accessory to ignition and your HU restarts and your music stops playing and the BT disconnects and you have to manually restart the music again? No such problems here

Turns out it has a capacitor that keeps the charge for long enough to keep it powered till I crank the car on, only the amp of the HU turns off at this time, but the screen and the rest of the board remains powered so that the connection isn't broken. A very useful feature i must say.
A few attached pictures.