I like the ProAcs too, but at the top of my list would be Silverline and Coincident Technology, as both are excellent and are about as tube friendly as you can get. I've also really enjoyed the Legend monitors at shows. Best of luck.
Well my Sapphire III LEs positively shine with my CAV 50. A big improvement over my previous Concertos. I am using a Titan II LE sub to take care of the very low frequencies. I have listened a fair amount without the sub, still a very good setup. The Sapphires are pretty easy to drive, very neutral with just a touch of sweetness, huge, multilayered image, really musical.