The MEC 600 came in 3 flavors, the original produced up until 1983. This model is referred to as the pre '83. The next version was produced for a short time until the Mark V was released. It is still a current model. Kits are available for each model. Ballistic Products (USA) is a good outfit to deal with, they ship to Canada. Bilozir in Alberta will import most of the Ballistic Products line.
A conversion kit will end up costing about $150. IMHO, I wouldn't invest that much into any of the 600 models.They were entry level reloaders, built solid, I still have my 600 Jr, pre '83 and it still makes nice ammunition. However, it will not deal with any shells with high brass. I believe the Mark V addressed that, but a much better press is the MEC Sizemaster. I have one in 20 ga and another set up in 410. I have a spare 12 ga kit, although converting gauges is not just a 5 minute job, so I kept my 600 Jr. A conversion kit for a Sizemaster is around $175.
When I acquired a 16 ga 870, I bought a LEE Load-All instead of buying another die set for my Sizemaster. I saved some money but I regret not buying a die set. You are on the right track.
Used sub 12 ga presses sell cheaper than what a kit costs, but they are not easy to find, unfortunately. One thing to keep in mind, as the gauge gets smaller, they get a bit more difficult to reload. 410 can be a challenge, took me a bit of time to set up the die set. My suggestion, buy a Sizemaster in 410, then make a decision on the die sets for the other gauges.
Don't buy any of the older pre MEC era brands, this one still haunts me, what was I thinking.