Despite other replies, what you're looking to do is quite common. Most brewers build their own.
Fast chilling and the addition of clean oxygen are both beneficial.
If you look at Sabco's BrewMagic site, they have a Chill-Wizard
that does just what you are looking for at $830. We could build you the same thing for $200 less.
Blichmann sells a plate chiller, not a counter flow and it's overpriced. Plate chillers can be had from several vendors at a reasonable price.