Even when you do find a card that will work with jumbo frames, I would recommend you only stick to regular jumbo frames (9000 or less) rather than super jumbo frames (9000 to 64K). It's not that they aren't ever used, but here's a good summary of "what's out there" that supports a particular frame size-
http://darkwing.uoregon.edu/~joe/jumbo-clean-gear.html
Basically most gear you are going to run into uses 9000 MTU or less, so you should likely configure your card to the same. Apparently at that MTU, NFS should perform nicely (it uses 8k packets.)
http://osdir.com/ml/os.openbsd.tech/.../msg00249.html
Happy reading.
