I don't think the reason so many Poo Pro's are for sale due to their lack of relaibility, but more due to the volume of Pro's sold and the refinements each model year.
That said I bought a new '12 Pro last month for a ridiculous deal, but it was a divorce sale.
Coming off a M1000 and still having a M7 I did not buy the Pro for it's reliability, in fact I don't really trust it (I do now, bit not in 1000mi form now). 50/50 bought it for the chassis and the great price.
If you only want '13 models, I'd say toss up between Cat and Doo for what you're looking for with the nod going to Doo so you could get a 600 and 800, his and hers.
If you want to stick with the same brand and want stable on trail yet good/great in powder and reliable, I'd look for lightly used or holdover 09-11 Cat M6 and M8's.