I highly recommend 'Hammerheart' by Bathory; it's by far my personal favorite of the Viking Quorthon era.
As for Enslaved, you can tell by the already-varied recommendations that people feel differently about their releases. The early Enslaved stuff is definitely much more raw and blackish, then they began to become the bombastic, wickedly epic Viking band that many love, and I cannot comment on their newer releases b/c I haven't heard them yet, though I'm told they're decidedly progressive while retaining only a trace of Enslaved's epic, Viking roots.
I say get either 'Eld' or 'Frost,' my 2 favorites. Good luck and happy headbanging.