Best mid priced Amp-Preamp

I didn’t look up your speakers. But with as little as $2300, the best bang for your buck that I can think of quickly is all Schiit: Freya Preamp and two Vidars run as monoblocks. That is plenty of power with a bunch of overhead. That is $2100 with $200 for delivery fees. I have had Vidars and they put out plenty of nice power. Better with efficient speakers though. I have a Freya and it really is great and great for the money. 

I had an Adcom GFA555 and GTP500. Needed work...

Replace them with current tech (digital included). I found a deal on the Peachtree nova300 for $1800. Bought some Ascend Acoustics CBM170S,$330 (and a used 8" sub). They will work till I can
 go around the country listening to better open speakers.

You may want to consider the Rotel integrated amps, the RA-1572 (around $1,699 new) or the newer more powerful RA-1592 (around $2,499 new).  The former is 120w/ch, the latter 200w/ch and each comes with a very nice DAC chip.  I own an older Rotel receiver and can speak to its durability and quality of build (like your Adcom products).  Each can be found used on Audiogon.

+1 on the Hegel H160. Also look @ Peachtree and Schitt. 

kns54 OP
  Please suggest best amp-preamp under $2000 for my KEF 103/3 reference series speakers.

A little more but this new John Curl designed Halo Integrated just got good raps put on it, not quite as as powerful as the older one which you could get on your budget, has everything even a Sabre dac in it. And would love your speakers.
JA's bech tests yet to come.
https://www.stereophile.com/content/parasound-halo-hint-6-integrated-amplifier

Cheers George