Please let me know what you think and the reasons why
It depends mostly on the graphics of choice.
At any rate, IME a more open case works better with a positive pressure setup (temp and noise wise), but so it will easily become a dust receptacle, so lots of effective dust filters (maybe magnetic ones) are mandatory.
I just purchased the gigabyte gtx 660 oc. Seems to be pretty quiet with the dual fans.
Yah, dust has always been an issue in my cases.
I don't know well Kepler's generation Gigabyte cards (while the Fermi's ones are often a bit less quiet than hoped), so I can't help and you will find out by yourself whether or not it's enough quiet.
Anyway, dust always build up, in positive or negative setups: in a positive setup you do need filters on intakes because the dust grow rate increase.
Providing you will find suitable air filters, I've recently transplanted a gaming system from an Antec Solo I into one of the last Antec One Hundred available: using a positive setup (three intakes, no forced exhaust) I was able to noticeably lower any temp except the idle VGA (given a similar noise level: take note that as I don't have any air filter for that machine, I reverted it to more traditional negative air pressure setup, dust will grow up the same but with a less wild ratio).
With reference to your needs, a GTX 660 is somewhat borderline: it isnt' enough hot to require a less restricted case, and as a matter of fact inside the Solo I there was an ASUS GTX 660 (now inside the One Hundred), where it ran cool and quietly even under load (I cannot hear it over the sound of two 800rpm running 120mm fans).
So, for a more power hungry card (to say, 170W and more TDP), I would rather a less restricted enclosure, but if you don't plan it, I think that a "silent" enclosure would be a more straightforward option.