recommendations for tube dampers???

The Audio Research clear tube damper rings have worked well in several units I have tried them in and are inexpensive.They seem to add greater clarity overall with better bass slam and texture.Results may vary with different components. I use them in my ARC gear with good results. I tried them in some Dynaco gear and the results were dramatic. They took a PAS pre amp and a ST 70 to a new level. This may be that the circuit boards are so flimsy in those units and they really need help in this area. Look for them at the Audio Research web site under retail price list, then go to the price listing for tubes. You can spend alot more,and I have not tried the ones you mentioned but if these don't do what you are looking for you are not out much green stuff. They seem to sell very quickly any time I have seen them listed here.

There was a little bit of chatter about a month ago on this forum. This is what I use to good and cheap effect.
http://herbiesaudiolab.home.att.net

I use the Pearl Tube Coolers on some of my small-signal tubes (as well as all of my power tubes), but I can tell you that though they seem to be effective at the job they're named for, they should not be looked upon as damping devices, and will in many cases add their own resonances to those of the tube itself. Sometimes they will shift a tube's inherent resonance in frequency, but will not absorb it, even with their woven synthetic jackets underneath the finned metal heat sink and the "rubber bands" around the exterior. Sometimes they seem to vibrate in sympathy with a particular resonant mode, and actually extend the vibration longer in time after the initial stimulus. Sometimes they do none of the above, and many times (in certain applications) none of this will seem to make an audible difference anyway. But with critical tubes in hi-gain blocks, another type of device is probably the way to go. BTW, I have found that I have no real way of knowing whether or not the Tube Coolers are actually extending the life of my tubes, but they do seem capable of rapidly acquiring and dissipating a high degree (ha!) of heat. The only other downside I have found is on the power tubes only, the very high temperatures involved will bake the "rubber bands" into a hardened state, rendering them useless when you have to change tubesets, so stocking up in advance is a good idea (try Michael Percy Audio).