OK, but it takes ages until The Music Resource (TMR) stock new items, and it takes them even longer to fill orders (though their prices are quite low), while Dusty Groove's prices are rather high compared to CDUniverse's prices.
I use CDUniverse most of the time, and TMR, Forced Exposure, Downtown Music Gallery and a few smaller companies (with higher shipping charges!) for "free / improv" CDs; I also use Deep Discount now and then: see my TMR comments above. A company I don't (can't) use is Cheap CDs, since they don't ship to Continental Europe.