Well I have some Phoenix Gold RSD comps on the way so I will let you know what I think of them when I get them installed. They cost me $129 shipped from an authorized dealer (onlinecarstereo.com). I currently have the Phoenix Gold Octane-R 69.0 6x9s as rear fill and they sound clean. i paid $54 shipped for the rears from
partsexpress.com. I am running them off of a Profile AP1040 4ch amp that I got for $100 shipped from millionbuy.com's
ebay store. That Crunch amp earlier would also9 be a good choice. Bought all my wiring from knukonceptz.com and then a few accessories from wal-mart.
As far as learning wiring, etc. check out
Basic Car Audio Electronics
I also have a cutoff for my subs so I don't use them all the time, and even though I have subs, the rear fill is still handy for when the subs are off or when i have rear passengers, and for a few 4 channel CD's I have. It is all preference though.
Anyway to do the cutoff for the subs put a toggle switch inline on the remote wire to the amp. $3 at wal-mart for the switch.
Also, you definitely will want an aftermarket head unit. I have the Eclipse CD3000 and I love it, but it is kind of pricey (~$250 but I got it with the car) I might be able to come up with some ideas for you. Kenwood, Alpine, Pioneer, Eclipse are all good brands.
I am still really new to this as the above is my first system, but if you want to know what I did or have questions, PM me.