Upgrade to Simaudio or keep my Classe?

In my opinion, Classe' has historically been a bit warm sounding gear. SimAudio, on the other hand, has been more neutral sounding.

I once owned both of these...Classé sounded warmer and refined, Sim: quicker, and more spectacular on short litening runs, but also dry and not involving musically speaking, listening fatiques comes quite early once the initial ''wow-have-you-heard-these-cymbals?'' effect has vanished. Don't mean to discourage you but, I feel going to Sim Audio might actually be a downgrade in this case, it all depends how you like your music.

Your components are good and appear to be synergistic with each other. Is there anything specific you are trying to improve on?
The biggest upgrades recently have been in the digital domain and that may be where you will see the most improved performance for your money. I would recommend trying a cd player/dac upgrade to something like Audio Aero Capitole or Electrocompaniet EMC 1 UP 24/192, or one of the other really good units (audition first).
I also own the Alon V's (MkII) and I have enjoyed the improved performance I have received by upgrading to the alnico HF and LF drivers used in the Circe, so that is a direction you might also try. I am currently trying different cables and would be interested in hearing more about the Dragons. I have Alon's Black Orpheus, which are good, but I think there might be better for SS equipment.

The W10 is a most definite upgrade. These are awesome sounding amps which will outperform esoteric amps costing much more than themselves. I once heard them in direct comparison to a Gryphon amp at twice the price and the Sims were as good. Sim audio stuff sounding fatiquing? Please... these amps are top of the line. I suspect it was your speakers or pre that was the culprit there. I have owned Classe 200, Bryston 3B, 4B, Levinson 331 and most recently the Sim W5, and I can tell you the Sim, at least in my system sounds much more musicaL, transparent with a wider soundstage than I have heard at this price level and well beyond. The W10 is again in a whole upper level.
Go listen to them, you must at this price point.

good listening.

I would have to agree with Arkio on this one. I just swapped out my CA-300 for the new Sim Audio W-6 monoblocks. They are a couple grand less than the W-10s, but a significant step up from the W-5. The W-6 are about 1K more than the W-5, but you get a serious 425W/monoblock @ 8 ohms. I also purchased the P-5, but can't give you much info since it hasn't arrived yet. Should be here this week.

Sonics are definitely improved on the W-6. There was nothing glaringly wrong with the CA-300, but I was looking for a more natural/neutral sound, speed, and presence. I got all of them.

When I store demo'd Sim, the system was Eclipse, P-5, W-5, Wilson Benesch Curves, Harmonic Tech interconnects and cables. It was an impressive setup, and I will probably replicate it at home, but felt that the system lacked some power (hence the W-6), and that I might try to find a pair of used ACT-One or Two instead of the curve for now.