When to put the amp in, ..now or lateR? Options

[amory_Tarr]

Alright, i just bought an alpine 9805 head unit to replace the stock GT tape/radio player. Anyways, i will be adding some form of a RF Punch Amp in in the near future and was just wondering if me and my dad were to put the head in, would it make a differance in finding a used amp to put in now, or is that something that would not be made easier or more difficult if i didnt put it in when i put in the head? Also, how much wattage should i be looking at? for xmas im getting a front component set that'll be powered by the Fosgate(im thinking either the 45.2, 55.2 or 75.2?) and then use the Alpine to power the rear two. Thoughts, suggestions?

Thanks,
Amory

[amory_Tarr]

Thanks for your help guys, that website is very usefull too! I don't know if i'd replace the rear speakers if i didn't have to. Would it sound good enough sitting in the front two seats with a fosgate powering the front and the alpine head powering the rear speakers and then doing something like fade a little to the back/turn up the fosgate to compensate type of thing. If i could get away with that then i wouldn't replace the rear speakers.

I am not going to use a sub, so i wouldn't need a 4 ch. for that. The only reason i'd consider a 4ch. would be if it would really sound that much better to have the rear speakers powered by 40W@4 Ohms RMS or 72W@2 Ohms RMS from a 4ch. fosgate vs. the 23W RMS from the alpine. But a few have commented elsewhere that that would blow out the stock speakers or push them too much etc..

The front speakers will be the Boston Acoustic Pro 6.5 Comp set which recommend a 20-400watt power amp, which is a pretty broad range, but i couldnt find their actual wattage ratting. One last thing, they are made to run at 3 ohms, but most amps are rated for 2 and 4, can you still run say a fosgate punch series amp through 3 ohms?

Thanks,
Amory