I wear yoga pants ALL the time. I work from home, so all I have to impress are the cats.
VS has some good ones. I also like some of the ones Nike makes (I buy them from the outlets for about $20). If you want to go super cheap, target actually has some for about $10-$15. They are super comfy, but they tend to fade in the wash.
ETA, from reading your posts, I think we have very similar body types, and I have found the Nike ones to be the most flattering.
i have a couple pair from gap body that i love. they have a wide waist band and are high enough that they don't slide down my butt (but still fairley low rise).