Spalted maple is generally a pain to work with. It is usually very porous, brittle and contains a lot of cracks from the fungal infections (that really is what causes the spalting). This means it has to be stabilized, usually with epoxy or CA before it can be worked on. Its a very time consuming process.
I hope Warmoth come across some more soon, as I know it is very hard to find good looking large enough pieces.