My opinion is that you have a good basic set-up. The weak link seems to be the Grado cartridge. Replacing it with a decent medium or high output moving could cartridge could be just what you're looking for with out breaking the bank.
A Denon DL-110 might be just the ticket. Your preamp has enough gain (might have to turn up the volume a little higher) to work just fine with the Denon. And it would give you plenty of money left over for a few turntable tweaks if you want.
A Denon DL-110 might be just the ticket. Your preamp has enough gain (might have to turn up the volume a little higher) to work just fine with the Denon. And it would give you plenty of money left over for a few turntable tweaks if you want.