I had a 2500A paired with the PV-14l MKII for awhile. The 2500A was a nice revelation to me. I eventually changed for a Coda class A amp that came along and made a very happy new owner of a 2500A. The 2500A is not the most neutral and transparent machine and it was designed as such. But in no way can it be considered lush or overly warm. Typical of the CJ signature 10 yrs ago. The power was more than enough to drive hungry Acoustat speakers so should be ample to drive the PRO AC. But the rooloff at both extreme frequencies might not bring the total resolution capacity of the 2.5s. And might also impose a limit on transparent pres like the Calypso. But all is a matter of taste and music preferences.
The PV-14 was my first tube preamp. It opened my taste for tube sound but it won't stand any comparison with the Calypso which I also tried in my system. Another pre that I tried with the 2500A is a VTL 5.5. It's signature was very much alike the PV-14 but with a lot more dynamics and resolution.
Considering your budget, I would aim for a former glory like a used Premier 17 which should mate well with the 2500A. The Calypso would also represent a good value, it is such a beautiful looking machine.
PS : Make sure the 2500A has enough air flow around to keep it from overheating. It is not a class A amp but it still needs air flow. Believe me, I blew up enough fuses to find out about it. Once I did, never had a problem with it, never again.
