You should up the video card from a 7600GS to a 7600GT, from a brand such as eVGA or XFX.
Don't be fooled by the 512MB of RAM for that 7600GS you linked to, it is not so good. For starters, it is GDDR2 instead of GDDR3. But more importantly, the 7600 series only supports a 128-bit memory interface. Having 512MB of RAM and a 128-bit memory interface is like trying to get a large tank of water out of a small pin-hole!!
First of all, are you planning to use your PC mainly for gaming? Do you want a gaming video card??
If you are interested in the GeForce 7600 series, I am currently using
THIS ONE, and it is pretty OK for the gaming I do (since at that time, I
could not push my budget for a 7900GS...
). This is the XFX GeForce 7600GT "XXX-Edition", which means it's overclocked past nVidia's reference design.
Another great one would be
THIS ONE. It is the eVGA GeForce 7600GT KO, which is also overclocked.
These would be superb choices fitting your budget of $150.
As for your power supply in that link provided, a few things...
The amps on the two +12V rails are good. Heck, dual 18A rails are amazing!!
But the bad part is the wattage. A mere 300 watts is barely cutting it these days for
any system.
In addtion, for
every model in the 7600 series, there is a label indicating that they recommend a minimum of a 350-Watt PSU for one of their video cards in a single-card config, and at least 450-Watts for SLI dual-video card config.
You will very likely need to replace that PSU for a graphics upgrade.
Hope I helped!