Seeking Advice: Power Supply for new PC

*I think I first posted this in the wrong section so I'm reposting it here*

I recently built a new PC about 4 weeks ago. Currently I have a Power Man IP-S350AQ2-0 (it came with the case). It says it is a 350W output switching power supplyhttp://en.wikipedia.org/wiki/Power_supply . To be honest I've been reading up some of the Power Supply FAQ, but I became a bit overwhelmed so I decided to make this post to get answers as well as some advice. As of now, I have;

Processor: Intel Corehttp://en.wikipedia.org/wiki/Intel_Core 2 Duo (E8400http://en.wikipedia.org/wiki/List_of_Intel_Core_2_microprocessors%23.22Wolfdale.22_.2845_nm.29 ) 3.00GHz 6MB L2 Cache 1333 FSB
Motherboard: Gigabyte GA-EP35-DS3L
Memory: Corsair (TWIN2X2048-8500C5) 2GB DDR2-1066 XMS2-8500
Hard Drive/s: 2 Western Digital (WD2500AAKS) 250GB 7200 RPM 16MB Cache Buffer
Optical Drive/s: LG (GH20NS) 20X SATA DVD Burner
Sound Card: Creative SB X-Fi XtremeMusic
Video Card: EVGA GeForce 7300 GS

Now, in less than a week I plan to buy an EVGA GeForce 8800GT. The 512-P3-N800-TR to be exact.
Can be found here: https://www.zipzoomfly.com/jsp/Prod [...] e=10008654

I've been busting my brain trying to figure out what to do. Am I ok with the power supply I have now or am I going to need a better one? Eventually, I'd like to purchase an Antec modular power supply, but because I'm tight on money (especially after I make this video card purchase later this week) I'm going to wait. Not only that, but half of the people I talk to say "you need more power!" while the rest say "you'll be just fine, you have more than enough." Because I don't know how to properly scale what I have as of now and because I've heard that calculators are not completely accurate for a task as such, I'm asking you all for your help. I'm sure I sound pretty dumb, but I can't know something until I learn it/have it explained to me. Thank you all for anything you can provide me with.

P.S. If this post is in the wrong category then I do apologize.

Thank you! Now the only question I have remaining after reading your post is this. Is the only reason you have a 1000W PSU because of the possibility of adding things to your PC later on? After looking at those specs and reading "Your PC will use more or less the same as mine." I started to become confused. If I'm good with a 400W PSU (as I have no intention of adding anything else to this PC) that's what I'll begin to search for. Aside from that, if my PC is going to use "more or less the same" as yours, then I'd think I need something more than 400W, right? >_<

This is what I have come up with, and I'm really liking it.
Presenting, the Antec NeoPower 430!
http://www.newegg.com/Product/Prod [...] 6817103939

I feel this should suffice my needs. Comments, advice would be appreciated!
Sorry for any misunderstanding. I just don't want to make the wrong choice.

And again, thank you very much!

A large psu usually have a high efficiency rating. Mine is 85%. However, you need to know that when the psu is stressed out, i.e. it's working at near its maximum wattage, the efficiency rating will drop. In the end, you'll waste more power than me. I'm using only about 1/5th of my psu.

BTW, I didn't buy mine at retail. It got dumped on me by a friend for CHEAP! How could I pass it up? His place is rather old, so is his wiring. Mine is not that old. His lights were literally dimming when he powered on the pc. Then one day, the psu blew his fuse.

Antec NeoPower 430 will suffice for your build.