Since with an HDTV cable box you can only send S-video or RF coax to your MCE system which are both in SD 480i format even when an HD program is playing so there is no advantage is using MCE to watch the sports programs which can be send direct to your HDTV from your HDTV cable box in HD resolutions.
Do you have two tuners or a dual tuner on your MCE system if not you can not support 2 STBs.
How about if you connect your STB to your MCE tuner card with S-Video and audion and to your HDTV with a component or DVI/HDMI connection. Not all STBs support both outputs simultanously so you might have to disconnect a cable or make a setup change in your STB depending on which output you want to use.
Do you have two tuners or a dual tuner on your MCE system if not you can not support 2 STBs.
How about if you connect your STB to your MCE tuner card with S-Video and audion and to your HDTV with a component or DVI/HDMI connection. Not all STBs support both outputs simultanously so you might have to disconnect a cable or make a setup change in your STB depending on which output you want to use.