I personally believe that for drivers having daily ride of 30-70 KM CNG is not a good option. I haven't installed it on my car too.
Bcoz at petrol you get Rs. 5 / KM average and I think you will get around 3.5 to 4 on CNG so its better to use it on petrol bcoz it takes you around 3 - 4 years to cover CNG cost so as to achieve equilibrium price and its better to save engine from CNG ( As discussed with MASTER AHMAD ).
Yes, if your driving session is long enough like 100 and above KMS per day then you might opt for CNG.
I am from Karachi so can't let you know about speakers market in ISB but you can add Pioneer or Kenwood normal range speakers 3000 - 5000 rupees to get a reasonable sound.
I installed JVC speakers in the rear which costed me Rs. 3500.
For wind screen cleaner fluid just stick to Honda fluid as it ocassionally require add on here in Karachi. I have got my car in September 2010 and have used only few times ( the wipers ).