Though Mr. Conner from Roadrunner Records suggests that death metal acts are no longer selling, this is not to say that some artists are selling very well, and growing in popularity. One of my favorite bands is Opeth, a hybrid progresive / death metal band from Sweden, who have reached Billboard positions, and have sold Their music can be described as a dynamic mix of early Led Zeppelin, mid-70's Pink Floyd, and older Metallica, but with growling. I highly suggest them, particularly the latest "Ghost Reveries" if you like intense, dynamic music. If you just like progressive rock, give "Damnation" a try - no growling on that album.
Several of Cradle of Filth's albums have reached gold status (100k) in sales, and most recently Dimmu Borgir's Death Cult Armageddon has reached 100,000 in sales in January 2006, according to Soundscan. Dimmu is (for lack of a better term) a symphonic black metal band, in that they incorporate live orchestra with growling vocals and guitars. Some of their music was featured in the original Hellboy trailer.
And, finally, I must say that Sirius Sattellite Radio's Hard Attack is very entertaining, with a good mix of all metal genres, including plenty of cookie monsters!