Don't go with the bose system. IMO very overpriced and doesn't give great performance.
Go buy a receiver, and start off with two towers and a subwoofer (2.1) when you have more money then get the other 3 speakers to complete the 5.1
Right now i have a yamaha rx-v365 reiciever which i love. It isn't high end but its great for its price. I have two Yamaha NS-777's. My subwoofer is a 10 inch 200 watt i forgot what name brand but i found it. It will be replaced with a subwoofer i just build on my own, a Tuba HT (BFM Tuba HT). It will do 20hz at 100db and louddddd as fck. Only down side is that its huge.
I would use newegg also