If you are not looking to spend huge money, belive it or not Pyle makes a few units that sound ok.
Get a set of 6x9's to match.
Amp wise I would get a 4ch. Run your four 8" off two of the channels, the 6x9's can run off the other two.
Don't mix subs with regular speakers unless you are going to seperate them with some kind of box under that bench.