While poking around for power supply options on another thread I can across this option that would work very well for track power, if you can live with fixed 18 VDC output.

http://www.mpja.com/prodinfo.asp?number=16684+PS

Using four of these, one per lane, would give you 18 VDC @4.2A per lane for $40.00 total. That's good enough for anything less than Unlimited for less than $50. You'll have to do some soldering and find an enclosure to mount them in.

you could easily convert that to variable, Ill have to dig up my link but it uses a LM338k 1.2 to 30 volt 5 amp regulator

here it is http://www.aaroncake.net/Circuits/supply.asp but this would be limited to the transformers output of 18 volts an 4.2 amps

Great Find! Too bad I already bought one... and paid way too much for it...lol

Dan