Standard Definition over Component on HD set

[JimSNJ72]

I have Snapstream 4.1 running on an AMD XP 3200 with XP professional and a Chaintech 6600 with 256 MB of ram. My tuners are a Hauppauge 250, Theatre 550 based card and an ADSTech over the air HD tuner. I have Snapstream connected to my Sony 36" Wega XBR800 Tube TV. All the HD content I play back looks great using the Nivida MPEG Decoder. I use it in Overlay mode as I get stuttering in 3d Accelerated mode. The question I have is this... is there any way to get standard definition programs to play full screen and auto change the resolution like my DirectTV hd box does. When I go to an HD channel you see it hicup for a second as it switches the resolution and plays the program in the native format. The closest I could do was setting a hotkey to cycle HD resolutions to 480i or 480p. Any thoughts?