Mjdraper, I used to own a Moon W-5 with my 10T's. The W-5 is an excellent amp in it's own right and in some ways was a real eye opening demonstrating the vast differences in amplifiers in general.
However, it seemed to me that the W-5 simply could not muster enough power and control for the bass and mid-bass regions of the 10T. But I could not put my finger on it. I assumed that the 10T's just demanded more juice.
Aside from the bass, it was far superior sonically to my previous amp, a BAT VK-500. But the VK-500's bass was substantially more powerful and controlling than the W-5.
I sold the W-5 and moved on. The next two amps confirmed my speculation regarding the W-5 not having enough power and control for the 10T's bass regions.
Then about 6 months ago, I stumbled across a review on the W-5 and P-5 products on SimAdudio's web-site. The reviewer was Peter Moncrief of IAR and as he praised the W-5 and P-5 for their overall excellent sonic attributes, he described in detail the weakness and lack of controlling power with the bass regions of the W-5.
He speculated on what the possible causes were. But more importantly, he confirmed that even though the W-5 has many positive attributes, outstanding bass region reproduction is simply not among them.