Well ofcourse it doesn't overheat... The heat is cause when the power draw is high. Maybe you've seen computer components that are rated to .. 130W for example (CPU) but you get 220W when you measure the power draw from the wall with a measuring machine and you think that 130W is a lie.. well it's not... cause most of the rest of the power from 130W to 220W turns into heat while the PSU converts Alternating Current (AC) to Direct Current (DC) The smaller this difference is, the more efficient the PSU is.
MB: MSI 760GM-E51 (FX)
CPU: AMD Athlon II x3 450 Rana @ 3,93GHz, 1,56 V
HDD: 1xExcelstor 160 Gb
GFX: Sapphire HD3870x2 857/1053
RAM: 2x2Gb Kingston HyperX Blu 1600 MHZ 1,65 V
PSU: Inter-Tech SL-700 700W