CD5750 might be right in the same league, if not a little better bang for the buck, although with higher entry cost. Crossfire 4850s will outperform 4770s, but the availabilty of the 55nm 4850s would, I imagine, drop off a lot faster than the 40nm 4770s. I haven't looked myself, but there has been some chatter about $99 4850s in recent posts.
Honestly I would not buy into the 4770 with the thought of upgrading later by adding a 2nd card. They will be gone or a new single card would completely outperform 2 of them. (oh wait that already happened)