ok first i have a question, do you want peltiers on cpu and gpu?
i juts put a peltier on my processor and i am getting load temps of 11°c and idle of -16°c
i have a maze 4-1 with a 170 watt peltier
also do you have anything in the way of water cooling gear already?
i am gonna assume not for now and see what i can get for 300
cpu block: maze 4-1 from danger den $50
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cpu peltier: 170 watt peltier from ebay (thermal enterprises)$10 or a "320" watt peltier for $17
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gpu block: maze 4-1 gpu from danger den $65
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pump: via aqua 1300 $18
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radiator: danger den heater core $30 or dual heater core $35 if you have room
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fans: 2 or 4 aluminum 120mm fans $9 each from jab-tech
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tubing,neoprene,hose clamps,and various other things lets say $40-50
if you get the 170 watt pelt you should be able to power it off most any decent 400+ watt power supply with atleast 16 amps on the +12v line.
if youy get the more powerful one then you are going to need a strong power suply with atleast 25 amps on the +12v line
and you should be able to power the 80 watt pelt in the gpu block with your main psu it takes like 7-8 amps at 12v
more to come in a little while.
you should check out what i did with mine.
http://www.ocforums.com/showthread.php?t=314362