I have two amps from my previous car:
alpine 3566 6 channel amp...power rated at 30wx4 at 4ohms OR 60wx2 at 4ohms

and

Rockfrod Fosgate 360a2.....power rated at 90wx2
all watts rated at RMS

I am going to replace the front components and the rear deck speakers. My question is what amp(s) should i use for this setup?

should I use the alpine to power all at 30w RMS (is that ENOUGH power????), and sell the fosgate, or should I sell both and get a more powerful 4 channel?

any help appreciated in this idle a/v section

ps, i will be upgrading to high-end components that are probably not the most efficient in the world, so power would be an issue, right?

 

I'd use the 90x2 for the front components. You want components to have a lot of power to sound good. The back speakers are mostly just for filler. With the back speakers you could go with something that's around 40x2. Some people even power the rear speakers with just a high-powered headunit which can run around 20 w rms (the stock in my 2G TL is only like 12 w rms). You could use the Alpine with the 60x2 output. 30 w is too little power for good components.

By the way, good speakers are not inefficient - you could run them on a 10w system and get it to be loud (but it'll sound like crap). It's about clarity and headroom. Even stock speakers will sound twice as good with a lot more power running through them... but they'll blow because they can't survive the added movement. So good speakers are actually more efficient than stock ones... cause they can handle the power without blowing up.