I have a Lee Classic Cast Single Stage (as well as a cast turret). I have both a Lee classic Turret and a Challenger press. I have a RockChucker. Can't reload .50 BMG on the RockChucker but you can on the Classic Cast. As nice as a Co-Ax is, it doesn't (nor does the RockChucker) make hunting ammo that performs any better in my rifles than the Lee Classic Cast and I can't see any sense paying almost triple the price for no noticeable change in performance, Id spend the extra in dies, accessories, or components.
Much like car sound systems. If I can't hear the difference between a $200 stereo system and a $2000 system, why would I pay an extra $1800?
Now, should I endeavour to enter the extreme OCD field of long distance precision shooting, I would probably need to step up on dies and equipment. Until then, my RockChucker remains permanently relegated to 2 duties: primer pocket swaging and bullet pulling (mostly bullet pulling these days).
I will actually give you that, if you're just loading up for hunting or plinking, pretty much any press on the market will do that job well enough to hit what you want to hit. My theory is, however, that if I'm going to go to the effort to make my own ammo, why not go to the small extra effort and cost to make that ammo as good as is possible? Why not ensure that every shot I take is going to be as absolutely close to the previous one as is possible, within the realms of my ability and budget.
having said that, if your budget says you can only spend 150 bucks on a press, then by all means, a used rockchucker or a new lee press will do you wonderful. if, however, you happen to have a classic turret, a challenger, a rockchucker, and a classic cast, then I don't see budget being a big issue. someone who was just starting off and wondering what press they should buy could simply buy a regular lee classic cast (for pocket swaging and bullet pulling, and 50bmg/other large cartridges if they ever got to that point), and a Co-Ax for everything else.
A coax does far more than a turret does - you get the ability to very quickly swap out your dies, but you also have the ability to move between a bunch of calibers easily and without screwing around with setup. I know you can buy new turret plates for your press, so fair enough, but the ease with which I can move between calibers on the coax is amazing, and the fact that it is also the straightest loading press there is on the mainstream market, one of the higher leverage presses, and one of the nicest to use, I think the money is well spent. It costs 315 right now from a company who sells these presses out east - your challenger and turret cost you about that much, maybe a little more I'd guess? plus you simply don't *need* the rockchucker if you've got a classic cast, though I totally understand having a bunch of presses, if the point is budget then the coax is a very smart press to buy if you think you'll end up taking hand loading seriously at any point in the future. buy once, cry once (and with the coax it isn't even crying, more like a gentle wimper).