Best tube mono block for 2k

See the Cary 572-se signature MKII monoblocks.

Myraj,
It would be in the best interests of everyone if you pointed out that you have Cary 572 monoblocs currently for sale.

You'll open up some additional opportunities for good sound at this price point if you'll consider a stereo amp; mono blocks at this price point are a huge challenge due to the inherent cost of manufacture across two separate chassis. Nonetheless, for mono blocks at this price, here are some options to consider:

Dodd Audio http://www.doddaudio.biz
50w ($1650 new) and 120w ($2600 new) mono blocks. Direct sales only keeps retail the price lower than you could otherwise obtain. I haven't listened to these, but several people whose ears I trust tell me they are very good, and fantastic at the price.

Conrad-Johnson Premier 5 - 200w mono block amps. A beautiful sounding amp, particularly if wired for triode. These occasionally can be found on the used market for under $2500 used these days.

Conrad-Johnson MV-5x series of stereo amps stapped for mono operation. Should be able to buy a pair for under $2000, depending on specific model.

BAT VK-60 - 120w monoblock (essentially a stereo unit strapped at the factory to mono) also selling occasionally under $2500 used.
.