Power supply - how big?

[pocino]

Hello. This is my first post (I have been eavesdropping for a while,
getting a wealth of information.)  I am about to start building a modular
synth. The first task that comes to mind is a power supply (+15, -15, +5).
My question is, how much current will, say, 10 or 20 typical modules draw?
My first guess is like 2-4 amps for the +-15, and 1-2 amps for +5.
Basically, I don't want to spend $862 on transformers, but I don't want to
run out of juice after 3 modules either. I imagine somebody who has
already built a modular synth or two could just say "yeah, use this much." 

Thanks,

Michael Pocino