Newbie needs advice - ~200 graphics card upgrade

[idalias]

SPECS for my Sony VAIO RB-50:
3.2 GHz P4
1.5 GB RAM
250 GB HDD
Pioneer DVD-RW
2 PCI slots, 1 PCI-e x1, 1 PCI-e x16.
3 fans total (1 in the PSU, 1 on the CPU, and 1 case fan)

PSU - 300W max
http://www.atxpowersupplies.com/300-watt-power-supply-bestec-atx-300-12eb3.php

I would like a new video card since i only have built in one (Intel Graphics Media Accelerator 128MB shared). For total upgrade, I was thinking of a budget of 150-200. I'll be using it for 3D modeling and rendering (ALIAS) I want this system to last me another 1.2 years (until I graduate).

I was looking into buying a XFX Geforce 6800 Xtreme for $100 with PSU requirements are 450W. Heard x800 gto with PSU 350W requirements.
So for these cards I probably would have to upgrade the PSU (perhaps XCLIO) ~50 .

So what do you think - should I
1. stick to a lower power card and save a litte money or
2. go with a better card and better power supply?

Will the performance difference be that big?

I'm very new to this so pls be nice only thing i've done with hardware is adding memory. Thx!

 

[nukchebi0]

I would get the card here:

http://www.newegg.com/Product/Product.asp?Item=N82E16814130021

Or Here:

http://www.newegg.com/Product/Product.asp?Item=N82E16814130020

That would still leave you with 70-100 dollars for a PSU, which you won't need to upgrade heavily with a power-efficient card such as this.