Whats this stuff worth if its all good? subs/amp/head unit?

Looks like it's worth what he's asking, and if you are getting your first set, those would be good. I would build a housing unit to put them together in one box, or 2 in one.
 
They aren't bad but I got a better set that you can have for the same price, just without a head unit. Its matching 12" Orion XTRs with a 1200 watt amp
 
im wary of that amp because boss equipment has a reputation to be faulty. i would want to try it all out first but those subs and boxes are worth $350 alone.
I would buy it and try and get a better amp
 
See if you can make a deal and try to buy the kicker sub in the enclosure and that kenwood deck . . . I wouldn't waste your time with that other garbage ! If he won't separate stuff then try to talk him down, buy everything and sell the rest of it yourself.