Amp for Proac Studio 140 mk2?


My current set up consists of the following components:

Wadia 121 DAC -> Anthem MCA-20 -> ProAc Studio 140 Mk2

I am looking to upgrade the amplifier with either an Integrated or a power amp (Wadia recommends that the 121 hooks directly into a power amp).

I am considering used equipment (and assuming that I can resell and swap if the sound isn't what I am looking for) and have a budget of $3000 to $3500. I am looking for something that will pair well with the Proacs and leave a bit of room for growth down the road.

Due to kids, pets, etc, I am leaning towards solid state, but I haven't ruled out tubes.

I have considered:
Ayre V5Xe
McIntosh MC252
BAT VK-255SE (pushing the budget)
Simaudio W-5
Krell S-300i

Any thoughts or suggestions much appreciated!

I recommend a pair of used Quicksilver V4 monoblock tube amps. Proac speakers pair well with tubes, and IMO especially Quicksilver.
I drive my 140's with a tube Cayin 100, and VAS tube monoblocks. Great sound, great value. Both provide better sound then solid state class a Marantz mono blocks, which I still have to drive ProAc 1SC's.
With the efficiency of the 140 mk2 you have the option of considering a class A intergrated, the Sugden A21 is a possibility. If you want or need more power consider a used Rowland Concentra 2. Of the amps you mentioned I would only consider the BAT but I would prefer the intergrated VK-300x due to the convenience of 1 box and 1 less pc/ic.
Any opinions on Pass Labs XA 30.5 (class a) or Audio Research VSI-60 (tube) with my system?

Also now considering VK-300x.

Thanks for the input!
Jdstrawn-ARC is widely accepted as a good match with Proac. I demoed the VSi-60 and thought the sound was thin and overly bright and there have been reliability issues with the VSi-60. IMO not in the same class as the BAT-300x. I didn't mention Pass Labs because at $3500 you would be hard pressed to find a nice 30.5 or int-30a. If you decide on a BAT-300x make sure you get a late model version(check serial#)with the 6922 tube.
I have also heard these speakers demonstrated with a Leben integrated. You should hear them with a Leben if you can. I think that is an excellent match. It has tubes, but none are exposed.
Thanks for all of the responses. I auditioned (in home) the VSi-60. To my ears it sounded great, but that could be due to the fact that it is such a jump up from the Anthem. I also auditioned the Krell (at the shop) and it didn't impress when put up against the VSi-60 (to be fair, the VSi-60 is much more expensive!).

I will be able to audition the Cayin stuff (but the dealer is waiting on a shipment). Anything else is going to be tough to get to hear.

I would really like to hear some BAT gear before I pull the trigger on anything!

Anyway, thanks again for the input. I'm really enjoying this process.