The fans you have are adequate. You wouldn't want fans blowing out the bottom of the case; fans at the bottom should be taking air in (hot air rises). Most cases you buy new that have fans at the bottom have the fans pulling air in. You seem to have a pretty good bead on things so I probably won't say much more. Just one question; the screenshot you posted from FurMark with the GPU @ 99%, how long was it running like that? If you're topping out in the 60s/70s with your cooler, I'd say you've had a success!