no-budget preamp?

Here's my situation: I just upgraded my CD player to a nice (albeit still low-end) Arcam. It sounds great when going straight into my tube power amp (a homebuilt job using mostly old Dynaco parts that has its own volume control) and my Spica TC-50 speakers. However, when I run it through the pre-amp section of my seven year old NAD receiver, the signal dirties up, I lose resolution, detail etc.

I want the convenience of the preamp for volume control, remote control, switching between sources, and the power amp does need a little gain on some cd's. But I've got literally no money. I know I have to spend something, but what's the cheapest option for a preamp that won't be a ruinously weak link in an otherwise pretty good sounding system?