consolidating 20:1 on servers is fantastic, my company is going heavily into vitualization and is only seeing about 3:1 so far (with the target being 6:1)
also, this sort of savings from virtualization assumes that you are running your prior servers lightly loaded. If you have an application that is large enough that you need to run it on multiple machines to start with, virtualization is a net loss (although this net loss is frequently covered by by doing the consolidation at the same time as a server upgrade)
I don't know about your servers, but on the ones I am seeing 8-12 cores with 64-128G of ram takes significantly more power than the 2-core servers with 4-8G of ram that I still have in production. measurements show somewhere between 2x and 3x