Hartke is cool. Requires some tonal twekaing but VERY usefull. Most EQ's on Hartke I saw boost some lows, cut the lower mids and highs. A 3500 head with 1x15 cab is great for double bass, and the 4x10+horn is killer on a MusicMan!
I know nothing about the heads, but there have been a bunch of complaints about failure of Hartke metal-coned drivers on the various bass-related web forums.