The instrumental is called "Seven", it should be the first song playing. Ignore the drums, they need re-recording.

Anyway, my problem is this: The bass is hard to hear on some speakers and the guitar seems very tinny.

Do any of you have any tips on recording guitar and bass? At the moment I'm recording right into my Mbox 2 and using Garageband. Any help at all would be great.
bass sounds great for me....some speakers just are not great at reproducing bass.....
my speaker system has a woofer so no problem on bass.

guitar does sound a little thin... Try using a compressor on it a little. Are you micing the guitar cab? or running the guitar direct to the interface?

if micing that guitar cab, get a nice SM57 and try some different mic positions.
right now im running the guitar right to the interface. ive tried micing the cab, but it came out sounding horrible. ill try some different positions. thanks for the help.