I agree with the puffin - stick with the 2000 series rather than go with the Kayanos
I haven't tried the Kayanos myself, but have used various models in the 2000 series (and I'm a neutral to mild pronator). The Kayanos are a much heavier shoe - the 2170 is listed as 265g whilst the Kayano 18 is 330g (on the Asics web site).
They are both "structured cushioning" shoes according to the Asics web site, suitable for mild- to moderate- pronators. The severe pronators are catered for with the Evolution and Foundation models ("maximum support" in Asics classification).
Personally, I've been happier since I moved towards lighter shoes (Asics DS Trainers and now Saucony Mirage) for my marathon preparation, and the kayano is the antithesis of the minimalist footwear philosophy. However, this is down to personal choice/taste, so may not be suitable for you.