Tube or monos for ProAc Response 48D

Having direct experience with pretty much the entire history of Emotiva amps, I would avoid the newest "Gen 3" amps (such as the XPA-DR1 you were considering). Your older XPA-2 is going to have much more bass power and will sound more natural than the new model. The problem with the new model is Emotiva’s decision to go to a switching power supply, which reduced the shipping weight enormously, but took a nose dive in overall sound quality (in my opinion). I have the XPA-DR2 in my own system and it just does not sound as good (even when highly modified and rebuilt). If you wanted a bump in performance, try upgrading the XPA-2 with better fuses (such as Furutech if you can find them, or something like BLUE. Isoclean is a possibilty too).  I went back to the original XPR-1 monoblocks, which just kick butt over the new amps and many others.

Thank you for the feedback. Looks like I need to find a nice pair of tubes to unlock the true potential. Although I live in LA, ProAc's are not ubiquitous to audition and decide. 

Thanks again. It helped me narrow down the list

 The Dynaco is a nice sounding amp, especially if it's been rebuilt. But if you're trying to decide between tubes and the Emotiva, I think you'll  be blown away by how much more realism a tube amp adds to the listening experience.
This ProAc is tube friendly, although you'll need some power since they are 4ohm speakers. The good news is most of the impedance curve is close to 8 ohms and will be easy to drive. A 70 watt Dynaco would do the job.
   But there are so many tube amps to choose from. Quicksilver monoblocks rated at 120 wpc may be over your budget, but I suggest you audition some amps and search the classifieds.

My friend uses these Quicksilvers with his 48D’s and the combination is outstanding!
http://quicksilveraudio.com/products/mono-120/

I would probably prefer the Dynaco although I have not compared the two. Currently using the Luxman MB-3045 on Proac D-40r speakers