Unfortunately no dedicated surrounds for the Platinum range - would be nice if there were some bi-pole surrounds.....
With both models having a similar driver array, they're not worlds apart, but there are differences/refinements when you move up to the PL200's. Obviously the higher frequencies are different between the two models, with the PL200's being sweeter with a more extended HF, giving a little more 'air' to the proceedings. With a more heavily constructed cabinet, everything's just tighter - the GS60's have some rather large side panels which will add in their own little bit to the end result. The Platinum's have as good a cabinet as you can get - solid, well braced, and not completely square, so less in the way of standing waves too.
Put on some close mic'd vocals and you'll hear the difference between the two straight away.
For what it's worth, I'd rather have the PL100's than the GS60's, and the PL200's are your next step up......