1) They have an infinity system and getting a after market radio cost too much to get it installed due to additional wiring. Or cumborsome to do it yourself?
This is plug and play. You buy this and an ipod and you're listening to your MP3s in a matter of minutes
2) They are no sure they can/ should use the factory amp with subwoofers that cames with the factiry radio on infinity systems?
This has nothing to do with the speaker/amplifier setup in the car other than you don't need to replace the factory radio.
3) Or they just simply like the look of the factory radio?
The uniqueness of the silver finish on our console makes most aftermarket radios look out of place and in addition to this, the radios that do have a silver finish on them that resembles the stock console are often very cluttered and hard to operate compared to the stock radio.
I am trying to find these answers because I didnt make it to the first ten people and have been asking around to get a nice after market radio installed and locak shops are trying to rip me off by telling me i need to by pass the factory amp, becasuse I have sub woofers and I need to buy and amp and a cross over.
Does this make sense?
You don't need any of this. The factory radio sends high-level (speaker-level) audio to the factory amplifier. The only thing you lose with the factory amp and an aftermarket head-unit is the ability to fade front to back which you cannot do with the factory head unit as the rear speakers are low-range anyways.
Hope this clears things up.