The above statement recommends 24A total for the whole system.  The GTX 460 will only use around 13A by itself under max load.  Your PSU is capable of 360W or 30A combined +12v power so you should be fine with a GTX 460 and a typical system.

I had a Hiper Type-R 580W for 3yrs, and while it could take a i7 920 at 3.6GHz, a single 9800GT at 750/1900/2200 overclock, my single VelociRaptor 150GB and a 3x 1GB DDR3-1333 kit; once I upgraded to a GTX260, it was unstable.  It wouldn't become stable without backing off my overclock to 3GHz or less.  Only a change in PSU to a CoolerMaster SilentM Pro 700W (w/ single 12v rail at 50A) helped me keep my overclock and my graphics card.  Note, nVidia lists the typical power of each card they sell, the difference between 9800GT and GTX260 is just 50 Watts -- also the difference between my CPU set at 3GHz and 3.6GHz.

A majority of systems components draw power from +12vdc, all of that has to be considered.  But nVidia knows most folks don't own power meters to tell if they need a better PSU, hence typical system power requirements on thei box.  Next time list your system specs for us to help you with that.  To say 'yeah a PSU works for a video card' is pretty vague and somewhat dangerous without considering the rest of the system, IMO. 

I'm not saying you need a new PSU, but PSU capacitors age and deliver less power over time (for my Hiper 580W, it dropped 4A on 12v in 3yrs, as system draw before was 26A on 12v) and other components draw power than just the video card.

tsunami231

Hmm this good question is would my Antec Neopower 500 12v 17a x3 12v rails be good enough for 460 SC, I trying to avoid buying a new psu till i have no choice

Currently I have i7 920 at 3.2ghz
6gb ddr3
9800gt stock speeds
1 HDD
3 92m fans and 1 120m

The PSU is rated for 38A combined +12v power which is plenty, give it a shot.

A 460W PSU?  Is the combined +12v power at least 288W?  This is NVIDIA's recommendation.  I personally wouldn't do it if it is a generic low end PSU.

Yes as lehpron stated, capacitors age and lose some power.  That PSU is right at the official requirements for a computer running a GTX 460.  So if the rest of your system is pretty mild, you should be okay.  But buying a new video card won't do much to an outdated computer.  Other components may need to be upgraded in order to benefit from a more powerful video card.

well here my specs:
cpu: intel core 2 quad q8200
mobo:Asus pq5 se2
case: sigma phantom

im wondering if 768mb is enough for 24" screen

ExplosiveBacon

well here my specs:
cpu: intel core 2 quad q8200
mobo:Asus pq5 se2
case: sigma phantom

im wondering if 768mb is enough for 24" screen

That depends on what you do with your video card and what you want to do with it.  You're not going to be playing every single game on their highest settings with good frame rates that's for sure.  You can try out a GTX 460 on your PSU, but don't keep that PSU for too long.  

Expect a slight performance increase - the GTX 460 is slightly faster than a 5830 in nearly every game according to reviews.  But be sure to completely wipe out your ATI drivers with driver sweeper in safe mode before installing the GTX 460.