Since you are mixing it up...
Since you are thinking about mixing presses (650 and 550) I would suggest starting with just one progressive (either one) and thinking about supplementing that press with a Lee Classic Turret press.
Here's my reasoning:
Getting two progressives right off the bat is rather expensive. Normally I don't recommend buying something with the expectation of trading it in in the future, but this case calls for an exception.
Learning on the Classic Turret will be simpler than learning on either progressive. (It is not impossible to learn on a progressive, just simpler working one stage a time.)
If you find the Classic Turret with auto-indexing is adequate for the quantities of your lesser-shot calibers you might not need the expense of two progressives.
If you find the ease of swapping calibers on the Classic Turret is to your liking, you might just want to keep it.
If you find the Classic Turret inadequate, the resale value is unlikely to be less than 75% to 80% of the new price.
Once you have used either of the two Dillons you are contemplating, you will be in a better position to decide if you want a second one of the other model or, perhaps, the second Dillon to be of the same model. Or that switching primer sizes is not that difficult after all.
I realize this suggestion may not fit your needs. But I think it is worth considering. Maybe even just starting with the Classic Turret alone. Like I said in my earlier post, at 300+ rounds per week, the progressive(s) are probably a better fit for you. Starting out with the Classic Turret might be a good learning step and let you pick which second progressive you want at a lower cost threshold.
Congratulations on taking the plunge.