Voodoo -
Apologies for the lack of swift response. I am not in the habit of re-visiting old crime scenes, but did tonight and your questions beg a reply.
On isolation, I have found it to pay real dividends. Some swear by an absortive approach, while others rate an attempt at direct coupling to sink away acoustic energy thought to cause electronic feedback. I have tried both with the CDT II, and have found the direct coupling approach to work best, using oak cones from Ray K's UK distributor Russ Andrews. Placing the player on a glass shelf makes it suck (now there's a trick!). It gets shouty and in-yer-face. Wood sounds best.
As for the magnetic clamp self-centering perfectly every time, no, it doesn't. Does it matter? I don't know. Sounds to me, in my system, like it may not, 'though.
I am afraid I know nothing about TACT amps. Best of luck!
K.