Class A Integrated amps

Stay two channel and look at quality integrated amps. I’d pick a Rogue Sphinx V3 for your speakers choices.

P.S. I don't think any of the receivers you listed are class a.

That Fisher receiver is tubes but not class A. A true class A solid state amp are few and far between !

That’s a really nice fisher amp if restored ie.recap etc. I believe its a class A/B amp though. If it was me I’d fully restore that Fisher and have some minor mods done like updated RCA’s and speaker binding posts. in the end its easily sold and you can recoup most of your money you invested into restoration. Fisher made some really good tube amps and this one is one of their best also highly desirable on the used market.

Marantz i don’t think makes anything that’s class A anymore, class A is getting rare in new production now. yes i know there’s some out there like pass labs, luxman, and a whole host of SET’s etc.

I’d try moving to better speakers first then decide if an amp is worth upgrading. i think the Klipsch speaker would be a good match too with the fisher.

Fisher 800C | Classic Receivers

If you are sure you are buying a Klipsch speaker then I would look

for a Luxman or Pass INT used with low miles. That will confirm for 

you that you were missing something. Even your Fischer will make the

new speakers sound good. 

Sugden A21SE is one to look at. The company has been around forever. Looks great and sounds great. Pure class A, 30 watts/channel.

Isn't the Fisher receiver tubed based? Klipsch speakers sound great with tube amplification.  Another option if not wanting tube amp would be the Pathos Classic One MKIII. It is a tube/SS hybrid. 

If sticking to a class A SS design then the Sugden would be a good candidate.  Also the Pass Int 25, though at higher cost.  Luxman made a model 550 which would also fit, however no longer in production. The Pass or Luxman may be found used. 

Best integrated pairing I've heard with Forte III's is Leben CS300xs.  It's Class A/B.  Sounds way better than a Sugden A21SE pairing which I have also tried. 

+1 on Sugden a21se signature a lot of amp for the money 

You are seeking to put racing fuel into an AMC Gremlin. Ditch the Advent speakers and make your following decisions accordingly. 

I agree with @laaudionut, Mike

+2 Sugden A21SE.  But then I do not know your endgame.  It's an overwhelming performer for Advent speakers, probably sold that model of Advent in the day.  Great performers.....for the day.  Any receiver would drive them and be musical.

The Sugden opens the door to a myriad of quality loudspeakers as it will drive most anything with aplomb.  I still own the older version and know its sound and capabilities.  I've run it with a JL subwoofer and Merlins.  It is so immediate with reproduction.  Versatile, F1 quick and nimble.  Have fun.  Cheers

I have the Sugden A21 (with phono stage) and it's a great integrated. I'm not sure if the A21SE comes with a phono stage. Anyway, both are fantastic and will last years and years. Let us know on what you decide.