Would you consider selling your amp and adding the $2k to buy a Pass Labs INT30.5? I think this is basically an integrated amp based on the XA30.5 and XP10. I have not heard it, but one advantage is having only one box. I have read a good review on the net.
Barring that option, I would consider an X-1. I used one with my XA100.5 before upgrading to the XP-20. It is not as good as the new XP generation, but it is within your price range and I have found Pass amps mate very well with Pass preamps.
There is also the FirstWatt B-1 buffer, though I would contact Pass to see if it is appropriate for your situation.
Barring that option, I would consider an X-1. I used one with my XA100.5 before upgrading to the XP-20. It is not as good as the new XP generation, but it is within your price range and I have found Pass amps mate very well with Pass preamps.
There is also the FirstWatt B-1 buffer, though I would contact Pass to see if it is appropriate for your situation.