Definitely get 'Seven's Travels' (I think it's their strongest overall album) and I also like 'To All My Friends, Blood Makes The Blade Holy' which is kind of darker, more chilled. Their new album 'The Family Sign' is also amazing - very very polished and smooth songwriting.
My current favourite album at the minute is the self-titled Doomtree album (who I got into after asked for a recommendation of people like Atmosphere), which has my current favourite track on it, 'Dots and Dashes':
Be warned, hip-hop is kind of addictive - you'll find one group then start listening to their side projects and find about five or six other groups you are into