to answer your questions:
3 vendors: Eastbay, Metalmaslow, MakerMade (no particular order).
I have both a metal setup and a makermade jumpstart kit and the newer due controller. I’ve used the M2 controller, but not the M2 sled. Metal advantage is no bricks are required and it is a much cheaper kit, but requires more build experience to get it right. Eastbay is the basic kit at a very good price. Makermade has the M2 with a z axis similar to the metal maslow, but they made a new controller that ads significant cost. I’m abbreviating this because it has been discussed on this forum in a few places. Each kit is based on the orginal maslow open source project that @bar made. In any case, it requires significant build time and significant learning for proper calibration, then additional learning to find “your” tool path to make designs as there are many many options. This forum will help you with suggestions on how to get through each of these, but this forum does not sell anything as Moose mentioned, it is for the users, by the users. When the kit manufacturers are not available to take your call, you can search here and then ask.