Spalt can be gorgeous.
Has to be said, though, a 5mm or less (which that will be) top of anything wont make much/any difference to the sound.
But spalt is most certainly not used for its tone. Its pretty, but it sounds cr@p. Full thickness tops of it will kill a guitar.
Disclaimer - this information is, stricktly, anecdotal; I havent played a spalt guitar, but the anecdotes are from Tim (whos played an 18mm topped Organic and said it was accoustically dead), several tonewood suppliers, Bob and Jonathon when I was thinking of using it for a top, so pretty reliable sources!