At your stated price range for new (15k-18k) and preference for ARC preamps, have you considered a ARC Reference 6SE?
It is the current-model ARC Preamp may be in your price range. The MSRP is currently 22.5K, and I expect you can find one in your price range, especially if you are willing to accept an store-domo unit (not a returned unit, which should be even less costly). Purchased this way, you should also receive the full factory warrant (which is value added). You may even be able to get the store to install it...
Reviews claim it is a significant upgrade over the Ref 5. I currently use one (see system photos), and I am very happy with it thus far.
Happy hunting...