[adithyagenius]

@sagarv, i dont know why you used 10% of electricity bill as saving. You should NOT use directly the difference of efficiencies to calculate difference in power draw. check the graphs of vx450 and the psu to find efficiency values at your cpu loads. The formula would be (efficiency of vx450 * electricty bill / efficiency of whatever psu)-electricity bill.
I also used to switch of monitor and speaker when downloading or away. But I used to game for 4-5 hours. The fact that 3870 system would draw more power than my setup which is too basic (first dual core ever) also would mean that 50% of usage as me would also lead to 2.5k+. This 2.5 times the price difference. so even if its further reduced 2.5 times and both are cost same in the end still it will be better to buy vx450 for silence and not contributing to global warming.