Thanks for all your help. It has not made my choice easier but it has certainly made it more informed thanks to your discussions.
I've taken an initial plunge and ordered a class B Cosmic and Sennheiser 600 from Headroom. The Cosmic is the old version at a doubly discounted price because the new ones will be coming out in 4 weeks and they used it as a demo at a show. The friendly fellow on the line said that I won't be able to tell it's not right out of the box. Given things people say about headroom I had no reason to doubt him. The price seemed right and I figured I can always send it back if it's not right. I might ask my local audio place to order the Grado RA-1 to audition and compare it with the Cosmic.