I have had SMGa, MMG, MMG-W, and currently have the MGIIIa.
I love thes maggies, but they need some serious power.
As mentioned earlier, run your fingers up toward the inner top of frames - it is here that the wires tend to de laminate.
I have rewired many SMGa and it is not difficult. Plenty of internet sites to show you how to do it. Google "SMGa rewire Peter Gunn" and you will find the best site. Just use a little bit of FRESH can of DAP Weldwood to glue them back down. If not glued down the panels will buzz. Using Weldwood, they will never de laminate again.
The only thing that can be a major problem is a torn mylar. I have had to scotch tape sections of torn mylar, and result was never perfect. You get a little buzz from the taped section. As far as a Tweeter rewire, I just used Rat Shack Magnet wire (36 guage?) instead on Aluminum. Work perfectly.
$140 is a great price as long as the mylar is not torn.
The crossover on the SMGa was a 1st order serial, not a typical parallel. Single cap and inductor. The serial crossovers are difficult to get right (critical on driver matching) but works very well with the SMGa.
The MMGs sounded brighter/clearer, while the SMGa sounded more warm and fuller. This could be due to the crossover differences.
If it were me and there were no issues on mylar, I would buy them and look into an active crossover (and biamp) and ditch the crossover altogether.
One caveat - You will want its bigger brothers very soon. And you may never want to go back to boxes ever again.