but I'd really prefer 1080p (I sit 7' from screen and have better than normal vision).
You're in a tough spot, no doubt. I absolutely concur with getting 1080p if you are 7 ft away with better than 20/20. For 6.5 ft is right about exactly where full benefit of 1080 is had with 20/20 vision on a 50". IOW, I vote S1 over the X1. The G10 is a nice TV, and I definitely understand the desire to at least check out THX mode. Perhaps you can visit a store, and ask them to put it on THX. Be aware it will be a lot dimmer than the other mega scorch mode TVs.
Now, if color accuracy is not that important as you mentioned, then THX mode with extra pic controls otherwise might not be worth paying for in your position. Resolution, definitely.
Look for the SM offsets recommendation PDF that I've posted here a few times. 7 pages, well written, for the S1.
I think for now, either sit still and wait until you can afford what you truly want (G10) or that some crazy sale happens (keep paying attn to Adam's posts, and maybe join forces with STRONGBADF1), or if you are less patient, I'm going to vote for the S1.
Regarding motion resolution, there will always be some sort of blur. Then consider that all of the TVs you look at apply 3:2. However, motion resolution is best on plasma for sure. The LCDs can match Panasonic, but only if FI is engaged for this spec. Pioneer blows them all out of the water, almost doubling Panasonic in this regard.