Why the 322 unless you want its 2 tuners for 2 separate rooms? With the 322 and 622 you would then have 4 separate sat. tuners (plus the OTA tuner in the 622) that could provide 4 separate programs to 4 separate TVs. Is that want you want?
I don't see any reason why E* wouldn't handle this as a single upgrade. The old receivers would only have to go back if they're leased.
PS - You'd have to run another sat. feed cable to the 322 to use both of its tuners. You might also have to do that with the 622 unless it's being fed from DPP equipment in which case the separator that comes with it will feed both sat. inputs from one cable.