Yamaha YHT-150 600-Watt 5.1-Channel Home Theater in a Box (Silver)
Great Product for Price
This is probabaly the best system that $300 can buy.  The only upgrade throughout the system should be all the cables (Speaker Cable, Subwoofer, Coax, optical, etc.)  I was looking for something basic and this system exceeded expectations.  Yamaha has good recievers so this system is easily upgradable.