My experience, coming in after installers usually, is that DirecTV is as bad, if not far worse, than cable these days. If you have a problem, you have to pay a technician to come out and diagnose it for you as they have zero customer support technicians in place to help you out.
If you can deal with that, then you can use any DirecTV capable recevier you wish and there is no price difference for service. I have heard good things about the Samsung DSS receiver. If I were to buy a HD-DSS receveiver today, that is the way I would go, and I would make DARN SURE that it included Tivo service. I have had cable w/PVR for a year now and can't imagine living without it ever again in my TV Land.