tube headphone amp?

I was just informed that I may not be able to get a headphone amp that I was seriously considering, the Audio Valve RKV Mk II. It's being "upgraded", (waiting to hear reviews + what the price will be). I'm currently using a MF X-CAN v2, so the only criteria are: it must be tubed, and it must be an upgrade from what I've currently got. So here is my short list, any additions/deletions? Let's start with a price-no-object list, I can whittle down from there: - The Earmax Pro; - David Berning Co. sells something called the microZOTL, but direct only; - that Cary preamp that Headroom claims is the best in the world; - Wheatfield Audio HA-2; - Antique Sound Labs - the MG Head DT; - Zeus OTL Headphone Amplifier by Fuchs Audio Technology; - Holmes Powell;