a cheap power supply?

[NotSoCoolJ]

You could use a large lighting transformer. You would have to rectify and filter the line but it's much cleaner and safer than using a number of PS units in series/parallel.
http://www.usalight.com/indoor_600_w...1_pr_1225.html
That one should be good for around 40 amps at 12 volts. Your rectifiers amperage should be rated for at least 2x the intended draw and more wont hurt. Filter capacitors should be no less than 36v for 12v or 60v for 24v. Again more is better.

What is your intended application? Do you intend on using direct contact with the cpu die or are you planning on making a chiller? ATX PSU's are not the way to go with big power TECs. Most people forget that the molex cable is only rated for about 6 or 7 amps. If you try to draw 30amps on a molex you will surely have a fire.