I am currenty using the SLO! I also have a 5150, Marshall DSL100 and a Randall BMF that I toy around with a bit. The SLO is my favorite along with my Randall BMF. I have been toying with selling the SLO for a Mark IV but do not have any experience with the Mark IV.
The problem with Mark series Mesas is that they usually sound compressed and stripped of some harmonic complexity and open-ness.
My real opinion is to sell off a couple of your least used amps, and come up with the money for a Bogner Ecstasy. IMO, it's a better amp than both of them. Use one for several years, like I have, and you wouldn't dream of trading it for a Soldano or Mesa. I wouldn't even trade mine for both of them as a package deal.
The problem with Mark series Mesas is that they usually sound compressed and stripped of some harmonic complexity and open-ness.
If I had to choose a desert island amp between an XTC and MV...it would tough, but I think I would choose the Mark V.
Yeah, I'd keep the SLO as well. I've heard people get killer tones out of both amps but I can't get past the complexity of the Mk. IV's controls.
Soldano SLO. There is nothing like the crunch channel on an SLO.