Thanks. Micah. The wall unit is made of heavy southern yellow pine, not oak. However, I do understand your concern about rattles, etc. This unit is solid, though. The pieces are made of 5/4 thick rails, stiles and panels, not thin stuff like you find in DIY stores. And it's glued, not nailed together.
I have a subwoofer on the floor right next to the wall unit right now, and bookshelf speakers of "the brand that shall not be named" on the middle side shelves.
Although I'm sure there is resonance going on, there are no audible signs of it. That may change with the greater bass response of the T60s. But, I suspect that oak would be somewhat better. There still would be some resonance, but at different frequencies and/or amplitude than that of pine.
The only reason I don't just go with the M22s is that I do enjoy MUSIC, and sometimes want to enjoy it in good old fashioned stereo without the distortions and phase problems inherent in a processed surround matrix.
Obviously, this would be an experiment. Who knows? It may work. Then again, the resonance problems may send me right back to the bookshelf approach. I could always put the T60s in my office.