Which do u think is a better power amp? Cary Cad120s vs vtl st-150?

Of the two I’d go with VTL. As a previous Cary owner, I’d say in my experience their tube amps are euphonic and tonally rich, but very hard to get endgame detail with. VTL will be more dynamic and resolving while still retain a good amount of musicality. Of course, this will all depend on the speaker you are pairing it with - what would those be?

Another amplifier to consider is the Margules U-280 SC 30th Anniversary amplifier. I became a Margules dealer last year after falling in love with the design and capabilities of their electronics. I have the U-280 SC amps set as monoblocks (can be used as a stereo or mono) and they are lovely sounding, full of soul and realism. They unfortunately are a higher retail price of $12K for one amp, but they can be endgame with the right speaker pairing. They pair with Raidhos at the shows and often get one of best of show across many reports. 

You’ve got two very different sound signatures there and not sure they’re substitutes, and I completely agree with @blisshifi assessment of the two. One of the big deciding factors for me would be that VTL’s customer service is legendary for being horrendous, and I’d never give my $$$ to a company that gives me the middle finger if I have a problem — too many other good options out there. I think ARC would be a great VTL substitute, and if you wanna bridge the gap sonically between VTL and Cary I’d give VAC a good hard look. I’d also highly suggest you consider the newer GaN amps from the likes of AGD and Atma-Sphere that seem to do a particularly good job of melding the best virtues of both tubes and solid state, and I bet the Totems would really appreciate the control. Just my $0.02 FWIW, and best of luck.

The 120S is really quite different from most other Cary amps, and comes across as a much more detailed sound. It’s not the typical "tubey" Cary sound (which I love).
Having said that, I’ve never heard the VTL you mention, so not a clue how they compare to each other.

You have a Cary Preamp so Cary Cad 120 would be a wise choice for ultimate synergy. If you’re looking for a change, consider Ayon amps. Like, Ayon’s Triton Evo PA amp. Based on my listening experience, Ayon is a much better sounding amp over ARC, VTL and VAC.

I currently running a Cary cad 120s in the system but I was offered a vtl st-150 for $2500 but dose the Vtl run in class A in triode like the Cary?

Many like VTL but their customer service is horrible towards people who buy used VTL.   Only company in 40 years in this hobby that I had a truly horrible experience with.   

I have had only a handful of failures over the years.  Most gear is reliable today , but if something does happen you want a company that is known for exceptional service.