Ben, the wickedGL drivers don't have S3TC support, they have a few options, such as "force texture compression" and "compression artifact somethingerother" which allows you to, essentially, adjust what and how much is compressed, i.e. you can find the best balance between compression amount and quality, so that you can elminate all artifacting
I, unfortunately, have had zero opportunity to do it myself.
I'd bet with about 99.999% certainty that those magic CD2 textures still are not accessible for the 5500
