I don't see how the TR coolers are really going to move or pivot much around the dimpled-center of the retaining bracket, even when you are moving the PC from place to place.
Aigo is "right-on" about the Core-Contact Sunbeam -- there are finally reviews (even in Russian-Cyrillic text [but you can read the graphs]) that show how it even edges out the Noctua -NH-U12P by a Celsius degree or two.
But if you are more worried about size, the TR Ultima 90 will work fine for a Q6600. Your over-clock settings will determine how much heat is dissipated. With the right G0 stepping, you should not be limited by the Ultima 90 any more than other coolers, even if it's second-place to the TRUE or even an edge behind the Sunbeam Tuniq.
Of course, my approach to this is to choose an over-clock that's still in the shallow side of the exponential distributions of voltage and heat rising with speed.
EDIT: MY mistake. I must've just finished posting some info for someone with a Q6600.
You won't have any problem with any of those coolers with an E8500 or E8600. Those cores are so scalable, you really shouldn't need to run the voltage higher than 1.3V or something. I have an E8600 @ 1.30V "set" and idle @ 1.26V -- clocked at 4.0Ghz and stable 16-hours-PRIME95 at 4.1 under the same voltage settings.
If you want to do "extreme" over-clocking, that's your choice, but you'll begin running up that steep exponential slope of voltages with an E8600 -- probably around 4.2 to 4.3.
EDIT AGAIN: You really add a chunk of weight to these coolers with your choice of fans. a 120x38mm fan on a TRUE addes between 200 to 250 grams, while the cooler weighs in at 790 grams. An Ultima 90 only weighs in at 460 grams. Personally, I duct my TRUE to a rear case-exhaust 120x38mm fan, and mount an intake fan to the rear of a hard-drive cage ducted to the front-side of the TRUE. With the Ultima 90, you only need a 92x25mm fan. You could even pull the Intel stock fan from a stock E8600 cooler, clip the push-pins, and adapt it to fit the Ultima 90. I think top speed on those stock fans is only 1,700 rpm. Not too noisy.