It is most likely exactly what you are looking for. Best of all, there is a 30 day free trial, so no real risk.
The Amazon MP3 store is completely DRM free. The tracks are extremely high quality (LAME VBR -V2 if you know what that means, if not, it is better than 256kbps MP3). They have almost everything available, it seems. A collection roughly the size and scope of the iTunes store, anyway (and includes more indie, classical, and small-label artists than Apple's does). And, best of all, their prices are generally better than iTunes (many tracks are $0.89 and albums are $8.99, though brand-new and hot stuff can sometimes be a bit more). Plus since it is Amazon, you probably already have an account there, and it is certainly not "locked" to this one player. If you decide to switch away sometime in the future to iTunes or Windows Media Player or whatever... It'll keep working.
It is NOT a subscription service though, similar to the old Yahoo! subscription service or Rhapsody. However, JRiver announced that with MC13 one is coming, if that floats your boat. I'm not a big fan of the subscription services because of the related DRM problems, but if you want it, one will be coming down the pike here before long.
Try it out. If you have any questions, just ask. This forum is pretty amazing if you use it.