Yes, mate the NuForce with a tube preamp.
If you can afford it, I would probably get the Modwright unit. I have yet to hear somebody say something bad and the few times I have heard it in a system, I very much enjoyed the sound.
If the Modwright is out fo your range, I would think about the Eastern Electric MiniMax. I haev compared the MiniMax to the MF preamp and the MiniMax was more 3D, had a better soundstage, and presented a more enjoyable sound.
One other possible choice is the juciymusic preamp. Haven't heard it, but somebody I respect owns one and likes it a lot.
Lastly, I am not a big fan of the AA preamp. I think it is colored and really hides a lot of detail, texture, and character of the music.
Hope this helps.
George