HI all!!
I am planning on upgrading most of the components in my PC

3.0 GHz P4                            =>  3.2 GHz Athlon 64 X2 6400
(2x 512Mb)kingston              =>  (2x 1Gb)  G.SKILL 240-Pin SDRAM DDR2 1066
Intel D915GAV Mobo             =>  BIOSTAR TForce TF8200 w/ NVIDIA GeForce 8200 northbridge
Radeon x1600 pro                =>  eVGA Geforce 9800 GTX (G92)
aslo:
2 Seagate  SATA HDD's  80Gb and 160Gb
2 cold cathode lights (UV)
DVD+RW  and CD-RW drives
4  80mm case fans
1 PCI card (soundblaster live!)

I CURRENTLY have a 3 year old 500W  Ultra PSU.    From my own calculations  (adding up Wattage requirements for components) I think it will be enough.  also I have tried entering these components into some online PSU calculation programs which have suggested about 450W. (not that i put much stock into the accuracy of them).
The current PSU has been very stable all it's life (not like i was really putting it to the test with my current setup  )


also,  any suggestions or warnings about the upgrade would be appreciated  (budget=> $550 USD)

thanks for the help!!Upgrading your power supply will give you peace of mind knowing everything is properly powered, and that your SYSTEM is not at the limit. Also it will give you the option to move to SLI if you are planning on upgrading to two video cards in the future, many older power supplys lack the extra connections required.I wouldn't replace the psu until it started showing problems. But that's just me. I have an old Dell that has been running Windows NT for around 10 years now (constantly on, too). But it's probably lasted this long because it's hooked up to a good UPS. A good UPS will preserve the life of any electronic components.I wouldn't replace it untill you need to.The online calculators are actually pretty accurate...
Buy a good name 650W and put ti in the closet til the other one dies...Well,  the thing about the calculator,  was that it recomended like a 450 W  and I was looking at some online reviews of the video card (9800 GTX)  and it displayed that under load that thing could suck up like 290 W  then plus the CPU says it's 125 W so I imagine under load that could probably take 150 W (as an overestimation to be safe)  which is ALREADY 440 W and that's for the CPU and GPU alone.  This is why i was worried.  I found a decent looking 650 W for like $100  on newegg,   it's a Seasonic,  which I've heard good things about.  I'd really rather save that $100  if i could.   So...  If i AVOIDED this purchase atleast for a bit.  and I try this new config. with my old PSU (which still seems quite stable and strong)  What would happen if the components under load did try and suck up more than the 500 W the PSU is rated.  I imagine it would crash the computer and restart it...   is there a chance of something bad happeneing.  I mean,  i could see that frying the PSU.  which i'd like to keep for other applications if I got a new one.  Is that a possible consequence?