Umm... try Windows Media Player... they sound fine for me.
Except the overworld one, the first note is missing.
And, uh, I use SPC2MIDI, because I have no musical talent whatsoever besides matching up similar-sounding instuments, so I just convert existing SPC's into MIDI's. Oh, and they don't repeat well if they're looped, because I just timed them to end at 3 minutes, heh. Yeah, I'm a lame musician. But, I do enjoy making these, especially for games that do not have many available MIDI's.
These aren't the best that I've done... some of my Chrono Trigger, FF4, FF6, Tales of Phantasia, Bahamut Lagoon, MMX, and Ogre Battle stuff is awesome, but this thread does not address them and that would be off-topic.
edit: to remedy that, I've made a thread in the Creativity outlet, so cheque it owt!!