My house is in the process of being built, so my HT is still a few months away. I can share a little bit about my experiences in searching for the right receiver. You're right that the receivers you mention are probably not the best use of money with your budget. They don't affect the sound as much as the speakers do, and they'll also be replaced earlier, so no need to blow the budget there.
When I started looking at receivers, I also was in the $1000-$1500 price range and considering the same ones you are. I've subsequently worked my way down to about $500, because that's what the Yamaha RX-V659 costs. There's a great review about it on Audioholics, though the main drawback is that it doesn't support HDMI switching. If you're going with a 5.1 system, then a 5.1 or 6.1 receiver may be a little less expensive than a 7.1 receiver.
One feature that isn't often prominently advertised in the product description, but worth looking for, is a set of pre-outs for all the channels, so that you can connect the receiver to an external amplifier. Your room is pretty large, so it's conceivable that you may need an external amplifier, at least for the front channels. The lowest-end models usually have only subwoofer pre-out, or none at all.
Another feature to consider is lip sync (audio) delay, which will help compensate for the possible video delay introduced by the video processing of the TV. I don't know much about the processing features of the TV's you're looking at, so this may not be an issue for your setup. Again, the lowest-end model receivers usually don't have this feature.
If you're looking for non-HDMI receivers, then $400-$500 is the sweet spot (in my opinion). Receivers that fall in this range include the Yamaha RX-V659 (and its twin, the HTR-5960), Denon 787 (I believe the AVR-1907 may be its twin), and Onkyo 703. I'm not as familiar with the HDMI receiver options.
Hope this helps (rather than confuses!)
