VT-100 MkII matches best with what preamp? HELP

Well, I have a Proac Res. 2.5 w/ ARC VT-100 MkII power amp. Now I'm looking for a suit preamp that matches my power amp and the speaker. Please recommend. What I'm looking for is not the most expensive one. I even want to buy a used one. Please advise. It'd be great if you can tell me where I can get a good deal on used preamp that you recommend.

Thank you