Best Class A Amp under $2,000 used?

Here's a pair of Aleph 2 monoblocks for $1,100: https://www.audiogon.com/listings/solid-state-aleph-2-monoblocks-aleph-2-monoblock-amplifiers-2017-04-26-amplifiers-33460-lake-worth-fl--2

100 Watts Class A

Your Dali's are 88 dB so 100 W would be more than enough to drive them.

OK, here is a pair of Bryston 7B-ST monoblocks that are slightly above your budget ($2,600):
http://www.usaudiomart.com/details/649345505-bryston-7bst-amplifier-pair-two-for-sale-as-set-only/

- 800 watts per channel with 1 or 4 Ω load
- 500 watts per channel with 2 or 8 Ω load 
- parts and labor warranty until February 2020  
- switchable between balanced XLR or unbalanced RCA inputs

These puppies will drive pretty much anything!