Benefit of Tube Dampers/Coolers on 6H30?

A quick search of the forums led me to the belief that the effectiveness of tube dampers and coolers is dependent on the tubes used.

I'm auditiioning an Ayon CD-2, and want to really hear what it's capable of before deciding to keep it (which I'm leaning toward anyway).

I'm curious about how beneficial dampers and coolers are on 6H30 tubes. And if they are helpful, which to use? I saw Mrtennis recommended the EAT coolers/dampers (http://www.elusivedisc.com/prodinfo.asp?number=MHEATDAMP)in another thread, and he stated they tamed some of the mid/treble glare in his unit, which is exactly the issue I have with the performance of the CD-2 right now. OTOH, it seems Herbie's halos (http://herbiesaudiolab.home.att.net/)are the most popular choice, although I sense the EATs are fairly new.

Then there are these, with a choice of brass or copper: http://www.audiotubes.com/damper.htm

These, which look very much like the EATs, but cheaper: http://www.partsconnexion.com/Advertising/audiogon/pearl.html

These for the *really* brave: http://www.realhamradio.com/liquid-cooling.htm

And I recently saw some coolers/dampers somewhere that looked like the EAT and pcX, but longer, covering almost the entire tube, although I can't find them now.

I'm a bit lost. Are any of these products superior to the others? Do any of them change the sound in different ways than the others? Would it be beneficial to combine products, such as Herbie's and the EAT on the tubes?

Are the 6H30 tubes so good they don't suffer from microphonics and other common tube characteristics such that the use of any of these devices would render little if any beneift?

Thanks to all for your thoughts.

HC