i've had success with keeping my systems a little on the small side as to not burn up the electrical. Currently has a sony head unit (52x4), 2 5.25 speakers up front (200 watts peak each), 2 6x9 jvcs in the back and a knockoff brand 300 watt amp from pepboys and 10" pioneer (700 watt peak) sub in the trunk of my wife's 73 charger. It doesn't bounce the stock alternator around and sounds great and I spent less than $250 to do the whole thing.

I'm trying something similar in my RR, looking at 5" infiniti up front, and RF 6x9's in the back with a 250 watt amp and 8" tube sub. SHould be enough for some thump but not enough to mess up the electrical.

My old bee had 2 15" subs and a 1500 watt amp...it took forever to get the electrical to work correctly..new alternator, voltage regulator, etc