I do not have the Pace booth, but there might be a flaw in your thinking. What type of filter is the furnace fitler in the Pace booth?
If it is just a particulate filter, you are correct and the proper order (from inside the booth to the outside) should be furnace filter, mid filter, poly carb.
If the furnace filter is an activateed carbon filter, the order would be different and you would want it to go mid filter, poly carb, furnace filter.
I mention this becasue if you ware going to use the booth without venting to the outside, you may want to look at getting an activated carbon furnace filter as it will do a much better job than just the polycarb at removing chemicals.
As for suggestions, I can't speak tothe 1530, but managed to pick up a 2025 dirt cheap and I like the fact that it is more open while still pulling a lot of air. Having two layers of carbon filters is also nice (though the price of replacing them surely isn't). Thankfully they will last a while with the volume of painting I do. The Artograph are definitely solidly built and give that feeling that someone knew what they were doing when they designed it. That said, when I was doing my research, the Pace came up quite often and a lot of people seemed quite happy with it. Like I said, my decision was made by an incredible deal on a model better than the one I was looking at presenting itself. I think you would be quite happy with either, so I guess it coes down to which one you like more.
Hope that helps.