I have a mol d'art but I bought it from Qzina, so I don't have any advice about buying from them directly. I do love my melter, it holds temper for a long time. I have the 6kg one. You will have to experiment with it, I find my thermostat is a little picky. To hold chocolate, I leave it at 34-35, any hotter and it seems to be way too hot, and any lower and it gets cold fast. I'm trying to say that mine has a narrow point where I find it workable, and the temp is higher than what I thought it would be. I think every thermostat will have its own sweet spot and you'll have to find yours.
Jean-Pierre Wybauw used the 12kg melters at the three day advanced chocolate class I took in Chicago last week (full trip report to follow in a couple days). He stated that you need to learn where the thermostat should be set for each individual melter as they will all be a bit different, and not to worry if it appears to be "off" what it should be.
He tweaked the thermostat in half degree increments to dial in the proper setting for each of the melters, saying that he turns it just until the heating light comes on and checks the result.
Additionally you need to stir it occasionally as chocolate is a good insulator and the top will cool off with the bottom of the pan still at the set temperature. He stated that the chocolate will slowly thicken anyway if left at the "proper" temperature because the crystals will propogate. He occasionally hit it with a heat gun to melt out some of the excess crystals. He said you could also raise the temp by a half degree at a time to keep the excess crystals in check, or add untempered melted chocolate.
Using this method he kept three melters in temper for the seven hour day with very little work. The initial tempering via the seeding method went very quickly as well. All that has convinced me to go the Mol D'art melter route myself. I have a Chocovision Rev2 which works fine, but is far too small for the kind of work I would like to do. My next problem is to determine how many melters I need...