Are the HR 20-23 the only HD DVRs that will work with DirectTV? Are there other brands out there? I've already got 4 HD receivers (2 DVR) from D* and am planning on having a 5th installed, but was curious if there's anything else out there. Mostly because my monthly D* bill is approaching $150 and with another receiver it'll proably be closer to $175 which is getting ridiculous (Yeah, I'm an AV idiot. But aren't we all?). Thanks.