Since you already pay a DVR fee the difference between a 211 & a 612 is $3 a month. The 612 can record 2 sat & 1 OTA program and as noted it is designed for one TV (kinda like your 722 when its in single mode)
The 211k is a nice unit. I use one and you can have 1 sat & 1 OTA program going at same time. There is no DVR fee so its just $7 a month but to use it with a hard drive (highly recommend it) you pay a one time $40 fee but it covers as many hard drives as you want and if you add another 211k down the road (or go with one to replace the 722 and its $17 extra receiver fee) that $40 one time fee covers ALL the 211's on the account