Keep the HR 24 & upgrade on the H24. If you have Whole Home you can still share between the HD DVRs. The only thing you might be concerned over is the fan & hard drive do make some noise which might bother you at night.
The B-Band converter is an in-line adapter which works with MPEG-4 equipment. You will find one usually just attached to the sat in on your receiver. Attached is a picture.