Your video card was designed to be an entry-level low-end video card, to just meet minimum requirements, certainly not for gaming.
It has a 160 stream processors and 8 texture units, runs on a 64-bit memory bandwidth bus. So you can see that it's really just for basic computer usage and viewing some video, not gaming or HD video. It's the stream processors and more importantly the memory bandwidth that is giving those WEI results.
Go here to read more:
http://www.anandtech.com/show/4263/a...vd3-meets-htpc
You could have spent about $110 and got a HD5770 with WEI scores around 7.2-7.6, depending on memory bandwidth and bus speed.
Remember though that WEI scores are not the "end all and be all" of the Windows 7 computing experience.
You spent the money on two SSD units, might as well bite the bullet and get a better video card too.
My system has the CPU as the 'low scoring' hardware at WEI of 6.6, and my RAM at 6.9. After next week that will all change with a new build though!