tube pre suggestion

Hi Everyone,

I'm currently running an all nuforce system with the P8 preamp and the ref 9SE (currently v1, soon to be v2) amps. I have this hooked to Thiel PCS speakers.

I'd like to dump the nuforce pre and try something else. I've heard that a tubed pre is the way to go with my amps...a buddy of mine who I trust heard the Modwright SWL 9.0 SE with the nuforce amps and said it was incredible.

I'm new to experimenting with preamps--my other system has a Krell integrated so I've never needed to play with in this area. Any suggestions on where to start? My budget is $1500-$2k, and I'm thinking used market exclusively to maximize my value.

Comments from the Audiogon Gurus are appreciated!