the s-5 does 1150gh about 460 usd on ebay + a psu
the sp20e does 1200gh about 480 usd on ebay. + a psu
the avalon 4.1 does 900gh the quietest of all about 2.52 btc + a psu
the three above use the least power.
pm me if you want an s-5 or an sp20 and a quality psu.
Well, according to the manufacturers.
S5 1155GH = 590W
SP20 1700GH = 1200W----------------Don't quote this as it is not accurate. Yeah sp20's are rated to do this speed , but my KIA FORTE is rated to do 120 mph. 1200gh at 650 watts is realistic
once you go over 1400gh it sucks power like mad. and most top end numbers are 1625 at 1200 watts
So if you're upgrading from possibly S1 or S3 you might be able to get away with your existing power depending what you got.