The ongoing monthly cost increase would be $12 per month for a total of $19. A $12 DVR/Whole Home fee (VS $7 you now pay) and $7 for the additional receiver you don't have now. You would also have the ability to record all four networks at once, still leaving two other tuners available, and HD in the second room. Keep in mind the Joey in the second room does not have it's own tuners (Unless you pay more per month for a Super Joey) so it shares the ones from the Hopper, but it can watch a different channel than is being watched in the Hopper room, and can access the hard drive for recorded programs just like the Hopper can.
The decision would be is the added technology worth $12 a month more, only you can answer that. The actual upgrade to get the equipment can be free with a two year contract, contacting Mike H above or one of the DIRT members here is the best way to get all the cost answers.