Does an underpowered power supply slow down the pc.

[engstrom0304]

Would a under powered psu bottlneck other components?

So would a i7 920 and 4870x2 be alright on a corsair tx 650

 

[engstrom0304]

i heard that a i7 and 4870 x2 needs a decent 850 watt power supply and a corsair tx 650 would be under powered.