Do you really think you will install 24gb of memory? Won't 12gb be enough?
I am not aware of a cheaper gigabyte mobo other than the ud3p, which will definitely not support 24gb, it only has 4 dimm slots. The p6t is $235 at most retailers, and offers 6 dimms, xfire and sli at 2x16.
It depends on the amount of money you are willing to put into a motherboard. Asus P6T Deluxe V2 is a great board, made to overclock well, it costs $300. Almost all x58 mobo's are going to have many expansion possiblities, with the exception of the intel base model and the ud3p, which are just the bare minimum.