QNAP's HD Station is the best option yet for a NAS as HTPC.
QNAP has announced a 12 bay Atom-powered rackmount NAS.
If you can get by with a few compromises, QNAP's TS-469L can save you some serious money.
Try iSCSI if you want to speed up the small file performance of your NAS.
QNAP announced an "affordable" rackmount 10 GbE NAS, upgraded firmware and a few other things at CES 2013
The QNAP TS-569 Pro brings Intel's D2700 Atom to a five-bay platform, but little performance boost over the TS-559 Pro II.
QNAP has enhanced the cloud backup capabilities of many of its NASes.
QNAP's TS-269 Pro can move files at near Gigabit speeds. But it could push the limit of what you're willing to spend for a two-bay NAS.