Tubed pre to go with Aragon 8008BB

My current equipment is Northstar 192 Transport and DAC, Aragon 28K Pre and 8008BB amp, Von Schweikert VR4SR's, and Gurellia wire throughout. I think that I am close to where I want to be but would like to try tubes to see if I would like the sound.
I think that probably my current pre is my weakest link and have heard that the pre is a good place to put tubes. I want something trouble free, used is fine, $3,000 is probably tops. I like mostly classical and rock. Any suggestions will be appreciated.