Do you need the gain of an active pre-amp or is passive OK?
If passive will work, Luminous Audio Tech. (LAT) makes a very good single input passive unit for $125 brand new. I think they have a money back offer too, but not sure.
For active pre-amps, Space-Tech Labs offers a single input tube pre-amp for $349 with a 30 day trial offer. This pre-amp has received some good reviews at AudioAsylum in the past. See the link and click on QA-001
http://www.space-tech-lab.com/PreAmpPage.html
I'm currently auditioning a pre-amp from Dodd Audio that has 2 inputs. I'll bet Gary would build it with a single input and bypass the switch. You can email Gary Dodd at
gldodd@comcast.net
It is a very nice sounding pre-amp and it looks really great too. It is $450, but may be less with a single input/output.
My $.02 worth!!
Enjoy,
TIC