I wouldn't lose any sleep over this.
The only thing HDMI has over component is the ability to pass 1080p. And, the only source for that new-fangled 1080p format is the two new Hi-rez DVD formats. You ain't gonna get 1080p from no STB, or even OTA transmissions. They max out at 1080i, and many are only 720 anyway. and, standard def TV, which makes up the bulk of what you're getting, only clocks in at 480 anyway.
IOW, if you can run component from the STB to the TV, you'll be losing nothing. Now. just run some sort of digital audio from the STB to your receiver and you'll be all set.