Jonsher,
FWIW. I wholeheartedly agree with the above responses. It would be a step backwards, or downwards, to substitute a receiver for your current very good system- like trading in your sweet sportscar for a minivan. Your audio system is fine and the OPPO solves your HDMI and surround issues nicely, so put the money into the new video setup. You may want to check out the new Panasonic plasma HD models, I read on a video forum, I think it was Videogon, that they supposedly bought and use the same technology used on the excellent Kuros plasmas from Pioneer, which recently withdrew from the HDTV market. When I was looking for an HDTV a few years ago, I really liked the Pioneer picture the best but the price was too steep at $10K. I think the Panasonics go for less than half this. Good luck.
FWIW. I wholeheartedly agree with the above responses. It would be a step backwards, or downwards, to substitute a receiver for your current very good system- like trading in your sweet sportscar for a minivan. Your audio system is fine and the OPPO solves your HDMI and surround issues nicely, so put the money into the new video setup. You may want to check out the new Panasonic plasma HD models, I read on a video forum, I think it was Videogon, that they supposedly bought and use the same technology used on the excellent Kuros plasmas from Pioneer, which recently withdrew from the HDTV market. When I was looking for an HDTV a few years ago, I really liked the Pioneer picture the best but the price was too steep at $10K. I think the Panasonics go for less than half this. Good luck.