Looking for power amp with warm, smooth sound

I'd look for other speakers. I had Monitor Audio Silver 9's for a few years and couldn't keep them when I started listening to two channel more often because of the the same problem. I've seen a number of posts over the past months about Monitor Audios and brightness as well.

I switched to Quad speakers, but that too took some mixing and matching with integrated power amps to get the right sound for my taste (Musical Fidelity amps doing the trick as I tried both the A308I and A5, both with great results).

Look for something with a soft dome tweeter (woven dome or otherwise).

Stay away from Rotel. That would be disastrous with MA speakers (I had that pairing for a time as well...).

Vandersteen and Quad come up often as "warmer" speaker suggestions. I only have experience with the Quads, which I'm more than happy with at the price point. MUCH better imaging, although I still found them a little bright until I paired them with a warmer sounding amp as well.

I'm not here to bash on MA and tell you to sell your gear, but I owned two pair of MA speakers over the past 7 years, both had the gold metallic dome tweeter which was the culprit (I originally wasn't listening to two channel much at the time I upgraded to the second pair...). I eventually tried everything, including different equipment (Denon to Rotel to Outlaw Audio to Musical Fidelity), nothing worked to cure the problem. They're just bright speakers, more intended for home theater in my opinion (which isn't esteemed...). I use Shunyata conditioning (Hydra) and good cabling as well and I agree with blindjim that cables/power conditioning help, but from my experience I eventually traded the speakers in on the Quads.

I honestly wouldn't spend too much money on cables or power conditioning if you envision upgrading equipment. You'll find yourself spending $500-$1000 on cables/power conditioning when you could just use that money on speakers or a new amp.

I haven't heard the Quad 12L2s, I do have a pair of 22L2s which have been wonderful for what they cost. Still tricky to pair with equipment, but much less bright than MA and just as revealing (much better soundstaging).

Once you're comfortable with the amp/speaker combo, it might be better to focus on cables. If you're getting great sound out of cheaper cables (with good equipment matching that YOU like), better cables will only further the benefit you've got from that good equipment matching.

I've gone through Cardas (Golden Cross, Golden Reference), Acoustic Zen (Matrix II and Silver Reference), HGA Silver Lace, Audioquest Panther DBS, Tributaries Silver, Monster Cable, etc. I've also gone through VH Audio Airsine, PS Audio Lab, Zu Audio Birth, Shunyata Taipan Helix and Python Helix power cords. All of these cords shape the sound one way or another (some for the worse depending on your setup/tastes). I seriously doubt any of the aforementioned will qualm an excessively bright amp or speakers to the point you'll feel satisfied.

Key word is excessive brightness. If the setup is marginally bright or you have a slight bit of etch, cables work wonders...as does power conditioning and adding/removing sound isolation....and speaker placement.