What amp to get.

I replaced my Parasound processor with a Sunfire TGP-5.
I would like to upgrage my amp.I have a Parasound 3x200 and 2x200 amps. I am thinking of a used Sunfire TGA-5400, a used Krell TAS or S-1500 or a used Dreadnaught II. I have NHT VT-2 speaker system would like to upgrade to Definitive Technology Mythos ST system. What amp would be the best to get.
I think you're fine with the amps. What about upgrading other parts of your system?