I can just only recommend to upgrade your machine with a tda 1541 chip. The first and cheapest modifation would be, bypassing your oversampling chip. It somehow opens up your stereo image as if the musicians always have been playing behind a curtain.
I was a bit sceptic myself at first, but you have to listen to it yourself to believe it. I would recommend to bypass it with a good silver wire, for the best results. You can look on the net for more info, keep us updated!