Welcome to TeamBHP amandeepmonga.
To start off i think you should test drive INDIGO Diesel and then FORD Fiesta and after that any petrol. You will find that Fiesta is just as silent as any other petrol sedan.
Though as your budget is 5 - 6 Lacs and you are not willing to go for a diesel car below are some pointers:
1. Swift: Maruti product, low cost maintainence, Good looks (leave the rear looks), Good performance and comes in your budget. But it lacks space and boot.
2. Getz: Hyundai product, every owner i know is happy with getz, low maintainence like Maruti, Good on space, looks are not that great and Performance wise not that good. But its ok to drive in city easily.
3. Tata Indigo: Only go for it if you are keen to buy diesel.
4. Aveo 1.4: Nice car, Good looks but it's a GM product so you might have problems. Gearbox and steering not as precise as fiesta.
5. Fiesta 1.4 EXi (P): Again it's a nice car, Not a looker like Aveo but its fine.. Has the best gearbox and steering in its class. event though its 10 BHP less than aveo, it's still same in 0 - 100.. But again maintainence is high and its a ford
6. Aveo UVA: New kid on the block. Can't say much but there is a review by Drfiter. You can check it here:
http://www.team-bhp.com/forum/new-in...olet-u-va.html
7: Hinda City: Too much beyond your budget. Leave that out.
Now conclusion comes that you will be installing CNG kit so will need boot space. Swift lacks it, Getz has it but not much. So if you can sacrifice the boot space then either swift or getz.
If you want boot space you can either go for AVEO 1.4 or Fiesta 1.4 Petrol. Though have a look at old Accent 1.5 and Ikon 1.3 Flair. Both are good and tested cars for years. OR if you can wait for 3 months then a lot of new cars are coming which might tempt you.
Just my $0.02