Hey that build seems pretty solid. If I were you I'd go with something like the AMD Phenom II X4 955 Its very easy to overlock, and slightly more "future proof". I know its a tad more expensive ($139), but my experience will tell you it's well worth it.
I guess 4-core vs. 6-core depends mostly on what Lightroom can take advantage of. Games are going to run well on either. What Lightroom can take advantage of might be a different story. And ... what about the next version ... will it be optimized for hexa-core or not. Good question. It seems folks on the Adobe forums are wondering the same thing.
I did find one benchmark on Gizmodo showing the performance of the X6 vs the X4 for Lightroom. However, there's is the higher-clocked 1090T not the 1055.
Hopefully my last question, all of you have been an immense help and I really appreciate it.
Out of these ASUS Mobo's, what is the major differences? Are they worth the $10, $20 difference in future-proofing, reliability, etc? The thing that stuck out to me was the addition of a second x16 slot for Crossfire down the road.