|I don't know where you're getting the info that the iXtreme X5620 has a 250 watt power supply, because I haven't found any info about that, unless you already have it or know someone who has one. It's certainly possible it does - brand name system builders tend to cheap out on the power supply capacity, but even so it's usually at least 300 or 350 watts.|
The video card you picked requires your system has a minimum 300 watt power supply, no minimum amperage at +12v stated.
I'm not an expert regarding nVidia video chipsets, but I think that's probably better than the onboard video on the mboard.
The power supply you picked is so-so at best. Someone supplied info at the link you supplied under the ad that says it has a one year warranty. I recommend you get a different brand with a longer warranty, preferably 3 years or more.
Someone supplied info under the ad that says the power supply is supported at the Compucase HEC group UK web site.
"Is there a manufacturers website ?"
Compucase didn't make the power supplies - they merely distribute them. It's difficult to find the warranty info if it's even there on that web site.
There are links on that site to other Compucase HEC group web sites.
The USA site has a Search feature.
When I searched using; warranty: one year
, I got a list of many power supplies.
When I searched using: warranty: three years, and warranty: 3 years, and warranty: two years, and warranty: 2 years, I got zero results.
So, seemingly - ALL their power supply models have only a one year warranty.
Eventually I figured out the Xpower power supplies are made by Powmax.
Under construction - useless .
A search using: powmax power supply
reveals they may fail more often than other brands.
E.g. Click on: read all 21 reviews
I think you should pick a better brand.
E.g. ATI recommends these brands:
nVidia may have a similar list.