I don't see why not. The last transformer I had to buy for our landscaping (use it more for security lighting) was relatively low power output and expensive (Malibu), but if you've got one already and its at least 50watt, I don't see why it wouldn't work. Power supplies used to be based on a transformer anyway.

Btw, I have seen and taken advantage of some really good prices on power supplies here in the FS/FT thread.