With the Oppo 971H, you really want to use the DVI connection. That means that you either need a DVI switcher such as the ones offered by Gefen, or you need to start using component out of your HR10-250 so the 971H can have the DVI input.

Balancing the sub is tricky business. I've used internal test tones and Digital Video Essentials in the past, but both approaches left me further tweaking the sub level to personal taste. I've had the best luck using my SMS-1's frequency sweep, but if you don't want to drop $600 to balance your sub trim you may want to try either DVE or AVIA and leave yourself free to adjust beyond either one.