Sure it is, if you never need it it's wasted money, that's a mistake in my book. If you bought a solid Intel rig three years ago you'd have a 95-130w CPU and a >200w GPU.
If you upgraded now you'd have a 77w (65w, really) CPU and 200w gets you a GTX680.
The only time it makes sense to me is if you are planning on buying a second GPU.
Otherwise, just sell the PSU (if you bought a good one, it'll have a resale value) and move up. Just like you'd be doing with the rest of the computer.
Fan noise wise, the only time the PSU is going to be stressed enough to crank the fan up is with a serious CPU+GPU load and guess what: It's a rare GPU that has a quieter fan than a good PSU.