Warning: monster post.
This post is long even for me, but I was introduced to death metal through Behemoth, too, so I feel obliged to help out!
'k, so, I'll recommend you some bands and albums that I really enjoyed in the early days (and for the most part, still do):
-Nile. While not stylistically all that similar to Behemoth, they definately have some "catchy" songs, and similar production. Most people I know who like Behemoth enjoy Nile, and vice versa. Recommended starting album: Annihalation of the Wicked. Listen to the title track for full Nile-ness; Lashed to the Slave Stick is a good example of their shorter tunes.
-Bloodbath. "Resurrection Through Carnage" has the vocalist from Opeth and "Nightmares Made Flesh" has the vocalist from Hypocrisy, two bands that most new metalheads love, so it stands to reason that these guys are popular. Resurrection is a bit Sunlight-Studios-ish in its production style, but Nightmares is very clean. There really isn't a bad place to begin; I'd recommend sampling both LPs just to hear the slightly different styles and vox. They also have an excellent pair of EPs availible, "Breeding Death" and "Unblessing the Purity."
-Skinless! I still love these guys. While perhaps a bit more brutal than Behemoth, they are the epitome of your request (catchy riffs, songs that "slow down and get really badass and groovy," a few different pitches of vocals). Their only REALLY good album is Trample the Weak, Hurdle the Dead, although the one before (From Sacrifice to Survival) that is alright. Listen to A Unilateral Disgust and Execution of Reason to get an idea of how these guys sound.
-Suffocation. I find that their good stuff is mostly on the early releases (Human Waste through Pierced From Within) so the production will not be quite as clean as the bands mentioned above. Give them a shot, I guarantee you'll warm to them eventually. Possibly the best DM band of all time, in my opinion. I'd suggest getting Pierced From Within, although Effigy of the Forgotten is also badass. Infecting the Crypts, Seeds of the Suffering from the latter and Thrones of Blood and Liege of Inveracity from the former are good samples of their badassery.
-Morbid Angel. I actually didn't get into these guys for a little while, but they're great and perhaps you'll get into them more readily; try Covenant, see what you think. God of Emptiness and Rapture are two cool tracks, although the former isn't exactly fast-paced.
-Also, while not death metal per se, I think you might like Anaal Nathrakh's "Hell Is Empty And All The Devils Are Here." It's catchy but also pretty brutal, with elements of both black and death- since you mentioned not minding BM vocals, I'd suggest picking it up. Check out the track The Final Absolution.
