Where to start.... First, there are a handful of 2A3 amps out there. I own one of them, a Moth Si2A3. They're out of production, but one or two turn up every year for sale. Wonderful amps - it took me over a year to locate and buy one. After Moth went under, the designer (Craig Uthus) started Eddie Current. I think one of the Balancing Act models can be ordered with 2A3 tubes. Check out his site and the Moth Museum there - I think you'll see much you'll like. Another designer in the same vein is Donald North. He produces a very nice 6H30 amp and I think he's working on a 2A3 amp for the K-1000. He is also into Audio Note (and has their 2A3 amp) so be sure to check him out.
If you do some DIY, browse the plans at HeadWize. There are some terrific tube designs there. You might also want to go back through Frank Cooter's posts and maybe talk to him. He does *amazing* work with all manner of SET/DHT tubes. You'll learn a lot and get turned on to the more obscure DHT tubes. He's a great resource.
As for headphones, there are plenty of expensive ones. The ones I think are pretty damned good include the Sennheiser HD-800, AKG K-1000, Stax Omega 2 Mk. 1, Sony R10, Grado HP-1000, and the Sennheiser HE60 and HE90. Stax has a new model almost out that I've heard good things about, too.
My beef with electrostats is that the amp options are pretty limited, expensive and very complicated. They do sound good, though. Personally, I like Frank Cooter's approach with tubes and lots of iron. Not cheap, but I think I'll eventually go in that direction for an "ultimate" electrostat amp in a year or two. We'll see, since I have a bunch of dynamic amps in need of building.
As for my rig, I usually run the Sennheiser HD-800 from an Eddie Current Zana Deux. That's a special amp. It's an OTL with low output impedance, thanks to the 6C33C output tubes. It's fast, detailed and neutral, but I think the 6SL7 driver adds just enough tube warmth to let you know you're not listening to chips. It's one of the best values out there and makes a fine preamp, as well.
Like you, I also love speakers. Lately, I've been running my ProAc Response 2.5 clones. I also have a pair of ESL-63s and everything but the cabinets for the Linkwitz Orion3.
You asked about a tough-to-drive headphone; that would be the AKG K-1000. They're earspeakers that fold out (very cool - look them up if you haven't seen a pair) that call for 8W of power. I like to run mine off the Si2A3's speaker taps. 3W is pretty good and they're delicious on DHT. The K-1000 also sounds awesome off the Audio Note. I think immtbiker has a K-1000 up for sale. You might want to check that out.
Anyhow, that should give you a few hours of browsing.
And thanks for showing up! The noobs are great, but I love it when someone who has been in the hobby for awhile shows up.