How much would a decent system run me with: 4 speakers, 2-3 subs, 2 amps and a deck?

depends on how loud you want your stereo.
deck- pioneer deh-3300 $160
speakers- pioneer $100
subs- 2 infinity perfect 12's $300
amp- jbl bp1200.1 (1200-1400 watts rms) $360

you probably are lookin around 1000 for a good stereo.

Nah, don't listen to him. You can get a good system for under 4-500.
Deck-$150
4 speakers-50
2 10" subs-100
2 amps-200

you don't have to get top of the line stuff, even the lower price stuff puts out good sound and still gets loud