I'm replacing a tube stereo amp this week with a pair of Canary M350 monoblocks. I have a set of 8 foot Cerious Technologies liquid ceramic cables and wonder if 4 foot long would make that much of a difference. I can't (nor would I) cut the cables I have now but wonder if comparable cables being shorter would make much difference. I haven't heard the amps in my system yet and have no complaints with my cables.

Well first off the cable needs to be long enough to make the connection. And perhaps you need to factor in excess for slack.
But, there should be no difference in audio sonics between the 8 foot vs. 4 foot cable length.
That being said Tube amps probably perform their best when used with the shortest cable possible.

Thanks Ozzy. I'll keep the cables I have. I was also concerned with vibration from the speakers if the amps were set too close.

If cable possess high capacitance, the shorter the better. Don’t place the amps directly on the floor, of course; physical vibrations transferred into the floor will travel right into the amp’s chassis (even if it’s a cement slab foundation, though they will be less severe than with a suspended wooden one), especially bad with tubes.

Isolating the amps from floor-borne vibrations is always a good idea. If you’ve been following discussions on that topic here, you may be aware of roller blocks, springs, and the great Townshend Audio Seismic Platforms and Pods. The makers of all the isolation products tout their products effectiveness, but users sometimes disagree ;-).

Thanks. I have wooden floors and will place the amps on 1.5'' thick maple butcher blocks. I have fat pads to place under the amps.I use roller blocks under my turntable that sits on a Symposium Svelte plus shelf. I may get a couple more of them to put under the butcher blocks in the future. The butcher blocks seemed to work well with the fat pads under the Cary Cad 120s amp I traded in.