Well, The 4 room limit can be over looked ,but not unless you have been a good standing customer for I'd say atleast a year. You could buy another receiver and hook it up, But you are at the lease limit.
The most you can lease is:
2 Vip 722 -2 rooms HD DVR, 2 rooms SD DVR. But again the Hard drive and tuners are shared.
4 Vip 211k - 4 rooms HD, But there is an option to hook up external Hard drive and you can record programs Like a DVR, With no DVR Fee.
4 Vip 612 - 4 Rooms HD DVR These are single room DVRs. They can record 1 show and watch another at the same time. Plus Record a 3rd OTA at the same time.
2 Vip 222 - 4 Rooms is also an option But thats Just 2 rooms HD,and 2 rooms SD.
Also the more Receivers, the more Fee's. For every receiver you add after the 1st one is $7 per month.
DVR fees Vary by package , But could be free, Up to $18 as well per month.
After you've been a good customer , You might get Offered a 5 Star upgrade, That will allow you to go over the lease limit, But it also requires a Credit card on file .