Hmm...
You've found that the Hyper212+ fits well into mid tower cases?
Someone I talk to online (who is technically oriented) told me his Q6600 was holding back his radeon 4870.
This may have been a bit of a mixed bag though, as I believe the game he quoted (StarCraft 2) was more fixated on processor horsepower opposed to graphical capabilities. His upgrade to a Core i5 2500K may not have had quite as much of an impact as he thinks. Basically he felt that the Q6600 was bottlenecking his card.
Yeah I've put a couple Hyper212+'s in midtowers without any issue at all. But then I've put a Noctua D14 in a couple mid tower cases without issue either, and its considerably bigger... Actually thinking about it, the only heatsink I've ever had size issues with was a Zalman that was too tall. Traded it out for a CM V8 and customer was very happy I did!
And yes a Q6600 will bottleneck Starcraft 2, because as you said its very processor intensive. Most games rely more on the card. But in reality its not the proc that bottlenecks a card, its the PCI Express lanes, and therefore on older machines, the chipset. Since on older systems the PCIe Buses are not directly connected to the Proc, they are always a bottleneck. But the last article I read on it (and I'll admit its been a year or two), it didn't matter much until the higher AMD 6000 series cards. Most of the 5000 and below never used much more than 8 of the 16 PCIe lanes anyway, hence why running crossfire/SLI on a x16/x8 (or the more common x16/x4) board didn't hurt you with those cards.
Personally, I feel (have no quantifiable tests, just opinion) that my 5770 performs at its max on my Abit P35 Pro and Q6600 @3.6GHz. At least, Sins Of A Solar Empire sure doesn't mind it with everything set at high, zoomed into the battle, with a fleet of ~1500 ships on my side and similar sized on my opponents... Lots of laser blasts going everywhere with wonderful particle physics. Metro 2033 doesn't care for it though, but then the 5770 is minimum recommended for that game, and it does play at medium settings....
All that being said, I really need an upgrade!!!
@ Elemental: If your not overclocking, stick with stock Intel for MiniITX boards. Else your asking for fitment issues. If you are overclocking, good luck as it may be just trial-and-error till you find a good fit.