I have not heard the metal SS drivers, but I really like the revs. If you want to try a metal-ish speaker take a look at the ATD Hypergraph Ti. Great speaker but not cheap.
I do agree that the Vifa is a great little speaker especially considering the price compared to it's SS brothers. But I still love the 7100/7000/6600 and plan to use them at some point in the future for a cost no object speaker.
I have heard good things about the HDS and have been meaning to pick up a pair but I just have not got around to it.