I am a real novice with HD and D*, but after reading many posts. It is my understanding that the PQ of most D* HD receivers are comparable. I believe the differentiating factor are the options the various receivers offer. But like I said, I am a novice so I may be sorely wrong.
Please correct me if I am making a false statement here.
This summer they all will be the same, Branded DIRECTV no more RCA,Samsung or Hughes. Thomson Consumer Electronics is becoming the manufacturer. From posts on AVS Forums the Samsung 360 is having problems. My Hughes HTL-HD has been very good except a slight audio problem with Dolby Digital.
SD quality maybe more a factor of the TV set and how it is connected than the receiver. If you are currently using an E86 you have the option of SD or HD output it does not do both at the same time. The E-86 will upconvert the SD channels to HD output so you don't have to switch back and forth this might affect your picture quality.