As for the prices of JBLs, PM Sam. Oops! He prefers email to PM these days.
You can go to SoundFactor somewhere in Lavelle road for buying JBL.
You can buy the compos and ovals now and power it from the HU for the timebeing. Later on, you can buy an amp and connect speakers to it.
I hope your HU has atleast 2 preouts so that it can be connected to the amp suitably.
As you've asked a Brand specific question, it may be very much debatable.
If you just want to know my take about your question of JBL vs HERTZ, my vote goes to HERTZ all the way. Yes, they were indeed better than JBLs of same price range. Remember, this is just my personal take.
dont count it as a judgement.