Use eBay and do searches for older amplifiers like PPI (Art Series), xtant X series, but only the ones that have the "X" at the end of the number, not at the begining, A/D/S power plates and P series, Soundstream, etc. I have something on eBay right now, and while I watch what is going on with amps I have seen some nice A/D/S ones go for about 30 bucks plus shipping. These are amps that were 500+ when new. The xtants are going for around 200 and they were 1000 when new. Even though amps wear out over a long period of time, they have no moving parts and they will last for a LONG time. Anyway, I should say break in instead of wear out.

As far as head units go I say go with a new one, no need to go top of the line there. Speakers you should also buy new, JL, Boston Acoustics, Focal, Dynaudio and do not have to go top of the line there either.

I am in the process of researching stuff to build a system, PM me if you want to exchange some ideas.