I'd go for the Ultimate Battle Packs first. I assume they'll be out around Black Friday like the Saga Shuttle was last year. They'll just be easier to get that way.
Though, everyone needs an AT-AT and I doubt those will outlast this holiday season. I can't speak for it, as I have two POTF2 ones and skipped the Saga release, but I've heard it's still a good buy.
Then again, the Advanced x1 TIE is only $20 and is a really fine example of toymaking even though it's already ten years old. I can see why this is a hard decision.
Found two Concept Snowtroopers tonight, as well as the rest of wave 6. I've counted it up, and I've spent about $110 on Star Wars toys since last Saturday.