YES, it is Really important.
i don't why people always want to go cheap on PSU :?:
That's a good question. Here are a few theories:
Because nobody is impressed by bragging about the PSU unless it's something like the PCP&C 1 kW, and some people buy their PC just to brag?
Maybe because they can't SEE any performance improvement from a better PSU (until the cheap one blows up).
Maybe they believe the power claims on cheap PSUs - probably the same mentality that leads to buying "1000W" stereo systems that run off of 6 D cells.
I agree with you, I always plan for my PSU to be able to outlast the rest of the system so if the GF9950GTX or the HD3900XTXTX come out with 300+ Watt consumption I'll be good to go. A cheap PSU can wreck your whole system in the blink of an eye.