I am thinking of getting a few Clark TST239 s. Can I power these with my 7700 or do i need a separate sub-woofer amp? Ive got 2 spare channels I could use since I don't really have room for 7 speakers.

No problem running the Clarks, they take 100 Watts. Note that they are full range (up to 17 KHz). If you only want bass Aura makes a bass shaker that goes up to 200 Hz for about 1/3 the price.

Bass shakers have always seemed like a cool idea but I've never pulled the trigger. Not certain how'd they blend with the rest of the system. I'd be interested to hear how yours turn out.

I ordered the clarks and a dayton subwoofer plate amp sa240. Ill probably install it over this weekend and configure them in various ways. I'll have to let you guys know how it goes.

I have the same plate amp driving my 10" sub. Start with the volume low because you're likely to have the 60 Hz ground loop buzz which seems to be caused by the third prong on the power connector. I defeated the third prong on the connector and the problem went away. I hear ground loop isolators on the power cord also work. Other than that, I've had zero problems with the amp.