If by "glass ceiling", you mean you're going to have to go into seriously diminishing returns, you're right. I've had Symphonic Line Rg amps and understand that Klaus uses the same basic configuration/chassis and has incorporated upgrades, etc. in the Odyssey line. I've had way pricier Pass and Perreaux SS and several tube amps that were way more expensive and I'm not sure that they were better in many ways.
You can go tube or stay SS, but if you think your amps are "bright" in any way, it's probably somewhere else in the system. Not to insult your gear, but to praise your amps.
I've swapped a lot of gear over the years and still remember a ML CLS and Unity Audio (speakers), Symphonic Line, CAT pre and Purist cable set up (with both sets of speakers moved in and out over a year or two period), as one of my best systems. The CLS in that system drove me crazy, as the resolution made so much of my record collection sound so bad, but the good stuff sounded fabulous.
It wasn't the amps.
Now, if you just want to change for fun, I understand that, but without hearing your system and doing a few swaps of cable, etc. to see/hear what the perceived problem is, I can't advise. I can tell you smoother, stronger, weirder, prettier, etc., but I think these are great amps and I'd be looking at upgrading or correcting somewhere else, but I am not familiar with your other gear in my system, so have no real reference point.
NB: A cable cooker has changed my entire approach to what I previously would have thought were problems with other components in my system, esp with a thin or "choked" mid range and uneven or restricted bass. Make sure your cables are really burnt in well b/4 judging any other components!
Flame away, guys!
