Same “rules” as always apply.
The big advantage over being a total starter, is that you now have a good idea of what your workflow looks like. You know if the software you have used with your MTP2 is right for you. You will have developed some wishes and some features that are must have.
1) Determine workflow = now easy
2) Determine software choice = stay with what you have or define what software would be better based on workflow
3) Determine budget = tricky one, since you are essentially wanting to upgrade to something with the same price as what you already own. You will probably have to look for something used to make that work
4) Pick 2 (max. 3) controllers that fit workflow, software and budget
5) Get some hands on time if possible
6) Make your choice
The likely candidates, imho, for for deck upgrade from MTP2 would be:
– Beatmix 4, pretty much only an upgrade in number of decks/channels. Within budget
– (Used) Terminal Mix 4. Within budget
– Terminal Mix 8, full fledged pro-level controller, decent price. No standalone mixer. Outside budget, within budget if you can find one
– Pioneer DDJ-SX2 (DDJ-RX if you want to go RekordBox DJ). WAY outside budget, even used
– A few others like the NV, MC6000 mk2 (really good for mobile DJs, less for controllerists and such. Also a little to a lot outside the budget
– Whatever our others would like to add
In general, with the budget you mention, I’d go for a used controller or the Beatmix 4. If you get something like a previous model, it should have most features you are looking for. If you buy new for 300-ish, it’s highly likely that some key new features are missing anyway.