It all depends on how you want to run your DVD output signal. Your TV may be capable of upscaling, or your DVD player. The important thing is not to mess with the signal too many times. I use a Denon 2910 and let it do the scaling to 1080i into the plasma. It looks ALMOST as good as the Hi-Def feeds off of Dishnetwork. I don't put anything else into the mix. Just run straight hdmi to the TV from it. Then optical to the pre-amp for movie sound. I'm not sure as to Receivers as I've never looked into it as an upscaling solution. If you want your receiver to be in the equation it will at least have to be able to pass what ever signal you are sending it. I don't think too many receivers will be as good as the TV or DVD player or dedicated scaler doing the job though. Oppo's are supposed to be good too and can be had for half the price or less of some of the other upscaling DVD players out there.
There's also these:
http://www.anchorbaytech.com/products/systems/supposed to be the end all of upscaling. A tad spendy though.
