I hope this is in the right area, its not specific to a show, but with my 8300hdc box, whats my best bet for picture quality with hd content? Should i have my box fixed at 1080i, and let my panny 42px60u plasma scale it, or should i have the box set to passthrough, and have the box change say FOX to 720p, discovery to 1080i, abc to 720p and so on?

Just want the cleanest, best picture possible.

A lot of reasons why, but the only way to know for sure, is to try the different possibilities and pick the one that looks best to you.

It will all depend on the equipment. Some TV's will scale better than the STB, while some STB's will scale better than the TV.

As mentioned above, try each scenerio and see what looks best to you!