Is it best to isolate??

I have never experienced "over dampening". Only with speakers, not components. Isolation will make a difference IF the situation calls for it. Heavy components, that have isolation designed into them, will likely not improve with additional treatments. Also, are you thinking of isolation from external sources OR from the same source? There is a difference.

You must decide if you like what various isolation devices will do to the sound of your system. Many say its best to isolate and I do use isolation, but I'm still not sure whether the difference they make is audible or a positive difference.

Isolating always leads to depression, or stems from it, for me..

Withe CDPs though I've found nearly anything you put under or on top of it, and what you place it onto does matter as changes will occur.

The 'flavor' of the change IMO comes from more than just those pods, cones, pucks, or balls in direct contact with the player. The rack or resting place plays as much a part too. Some simply buy platforms for players. Simple.

I like the herbie's Audio Labs wooden Ebony balls atop the iso cups so far as the best I've used. Jesus I am cheap come to think of it. $60-$75 for 3.

Like Stan said though, and I've heard from a LOT OF OTHER PEOPLE those roller cups are a viable solution.

Find those folks who allow a trial term and get startted trying 'em out.

Good luck.

You might look into NOS Reflector 6H30-DR in the output stage, my experience is they are much better than Sovtek 6H30p. I haven't used them in an ARC product only my C/J pre where they made a big improvement.
Personally I would go for the tubes first, at least research them, then deal with leading edge grunge with isolation second.
The ARC equipment I've had,CD3 MK11 and VS-115, didn't need much isolation so be careful not to over isolate and lean out the sound.

Aurios MIB's under CD player work very well to improve resolution and bass. I have used them for years under CEC TL-1x transport with excellent results compared to nothing and other isolation/anti-resonance devices.

Neal