Hello Tony,
I'm gonna probably throw you a curve ball here, but here goes.
I don't hear 'muddy'. I hear something else. But first, what I think is muddy. Give this link a listen:
http://www.ketronus.com/sounds/SD1_4.mp3 This is from the Ketron site here in the US and the demo is called "Blusy". (48K bps)
To me, that's muddy.
Okay, now off to Italy and here Ketron's sample of the same demo:
http://www.ketron.it/mp3/sd1/blusy.mp3 Same thing but done up at 128K bps. Much better, wouldn't you agree?
Now give yours a listen to:
http://members.sniffout.com/nsymon/PrettyDresses2.mp3 To me I hear somewhat thin, bright, and some hot sibilants. But don't get me wrong, I like the recording. I like the rag-time piano...Sounds like you are having a lot of fun.
Regardless of what I think, I don't have any suggestions for ya because this is one department I haven't figured out yet either. When I record my keyboard digitally, I end up with recordings that sound like that first Ketron sample. Muddy, subdued, lifeless, BLAH!
Hopefully somebody can help you here and they post their answers for us 'recording-challenged' folks.
mike