We've used the Martin's MX1 (smallest version of the MX series). Very simple to use and good quality for a reasonable price. Multiple units can be slaved to one master light while using the built-in mic of the master for controlling the others via DMX. Or you can control all very easily with a simple DMX controller. The downside was the low light output level and the color & gobo quality are not the best.
We went back to PAR64 cans with DMX dimmers/controller but would consider the MX10 if we determined that the light output and color & gobo quality were better than the MX1

I'd keep the Trackspots and invest in HogPC, as half the usability of your lights comes from good programming. If you want to buy into current gear then go ahead, the Martin MX series isn't too bad, but I haven't heard much about reliability since they are a fairly new fixture.
Trackspots are great, parts are still available from a number of sources, and once you get them working in top shape they are very reliable. The lamp is cheap to replace ($8 compared to $100+ on some newer fixtures), very simple and straightforward light. Depending on the condition of the ones you have, if you spend a little on repair and maintenance, they'll run trouble free for a long while.
The only other small moving mirror fixture I like is the Clay Paky Miniscan HP3, but they cost a bit more.
I understand the set and forget mindset very well. It is hard to pull it off inexpensively though. The audio trigger mode never gets any points in my book, the results are totally random and don't ever work well with the music. I have yet to sind a simple, useful, idiot proof controller that is relatively cheap. The HogPC is the best I've seen, but you do have to program it and using it isn't always straightforward, but it does aid in creating a much better light show. There are a few other pc based controller products out there, some good and some bad, a lot depends on budget.