preamp with the Winsome labs

I have a small and great sounding set-up (considering the $) made up of the Winsome labs amp, an Oppo 980 and a pair of the new Role Audio Sampan FTL's-
I want to add a small sub and want a small pre with a line out for the sub.
Any suggestions?
I'd love to have a tube in there and want to keep the size and price (less than $400 new or used ) down.
thanks - Adam