In your factory fitted set up, the HU is connected to a Microsoft Blue&Me box that is located in the glove box where you insert the pen drive. Let me clarify a few things first: 01. When you change the HU, you lose the function of Blue&Me system. Now, you will depend upon the bluetooth and voice command system of the aftermarket HU. Yes, after market head units also have voice commands and bluetooth. e.g. http://www.snapdeal.com/product/pioneer-dehx4690bt-car-stereos/850789038#bcrumbLabelId:311 02. You can retain the factory fitted steering controls by getting a Connects2 steering interface for that particular brand of head unit. http://www.ebay.in/itm/FIAT-Punto-Steering-Wheel-Stalk-Control-Lead-CTSFA004-/250560245938 Integration of new HU to existing set up. You will have to replace the factory fitted head unit with an aftermarket one and use a Canbus interface like the Connects2 mentioned above. This will allow you to use the steering mounted audio controls. You will lose the Blue&Me system though and will have to use the Bluetooth and voice commands of aftermarket stereo. Also, please note that factory fitted mic will not work and a separate mic will have to be installed at some location of your choice such as A pillar. Please note that it is not possible to do this in the budget you mentioned. A Bluetooth equipped head unit won't cost less than 6k for sure and this steering interface costs around Rs5k. Factor in other charges like installation charges, ISO adapter cable, antenna cable adapter and stereo fascia/panel. These 4-5 things will cost you around 1k taking the total to 12k or more.