If you need to use an HDMI connection, you would want a Slingbox 500, not a Slingbox M1. The reasoning for this, is simply due to the fact that the Slingbox 500 is the only unit we sell that actually has HDMI IN/OUT ports. Be aware, if you only use HDMI with a Slingbox 500, you could run into copyright protection conflicts with your set-top box. Here is some further information on this particular scenario:
Hope this helps!