Speakers
Most big box stores have a 30-day return policy, so you may still have time.
I would not recommend the HTIB (Home Theater in a Box) type speakers at Costco, Best Buy, Circuit City, etc. Companies like Sony, Yamaha, and Pioneer are electronics manufacturers and are not know for their speakers. Also, small satelite speakers with 3-4" woofers are not capable of producing the mid and bass frequency ranges.
Start checking out some speakers at local B&M dealers like Paradigm, Klipsch, PSB, etc. In your budget, internet direct companies like AV123.com, Axiom Audio, and Ascend are also good options. Reviews on this and other sites are also a good place to start.