Hi Dave Welcome,
If you decide to swap the 59s (I would be surprised) let me know. I just bought a 150 and will probably move to the 59s from the current pups.
Tully, how do the Seth's sound on low gain?? I bet they are pretty sweet!
You have to check out a RT 2/50 and an RM4 if you get a chance, if you like the Mesa I am sure you will like the Randall stuff.
I wonder how a set of Mustaine Actives would sound in the H150, would that be sacreligious?? They are voiced like 59's on steroids, I have a set in my Dean Hardtail, a little dark at times, very musical though and a hell of a bite. What are the thoughts on actives in these fine instruments?