Let me say off the top that I'm a total audio newbie, and I don't need surround sound, and I'm not trying to create a home theater experience.

I have a nice sized HD television (about 2 years old, currently connected to an old SD TiVo, and standard def DVD player, so there's no actual HD). I've been using the standard television speakers for a couple of years, and they are just not cutting it anymore.

I don't want to spend a lot of money, and I'm no audiophile. My question is, what should I buy, how much should I spend at a minimum, what the hell is a receiver anyway and do I need one, etc.