Enjoyed your impressions minimus! And I really hope this isn't the end of L-2 production, given the info songmic received. Since first learning about the torpedo and then the L-2 on HC and innefidelity, I've been keeping an eye out for an opportunity to hear one. I'm all the more interested having recently completed my bottlehead mainline, which is a fairly similar parafeed, single gain stage, constant current loaded 6c45pi wot amp - the derivative of a bottlehead statement piece from many years ago.
Tomb actually noted the similarities in another thread when discussing the virtues of well implemented output transformers:
OK - I'll chance getting this deleted as shilling my own product, but seriously - there's an easy answer to your question: there are many pure tube amps available. As someone else mentioned, you need output transformers to handle various load impedances. That's the only thing that can be made to equally match output between the extremes of 300 ohm Sennheisers versus 32 ohm Grados.
Mapletree makes fantastic stuff using this principle. There's also an excellent amp called the L-2 by ECP Audio. Tyll mentioned it on innerfidelity.com when he was reviewing the Abyss. He had the L-2 paired with the HD800's, and stated in so many words, that it takes all the high-end harshness out of the HD800. There's an offering on Beezar (me) called the Torpedo, also designed by ECP Audio - it's primarily a DIY-kit. It's a parafeed design, which is a term used to describe how the output transformers are connected into the circuit. The Bottlehead Mainline is also built on the same principle (parafeed). Notably, the L-2 and Mainline use the same signal tubes - 6C45's.
Just MHO, but output transformers - even relatively cheap ones - blow away the output coupling capacitors in OTL amps. There's no comparison with the transparency and detail. Output coupling capacitors put a fog over the entire music signal.
Mods, please delete if this was inappropriate.
Based on Tyll's comments, among others, I suspect the mainline and L-2 share a lot of sonic similarities in terms of making for an excellent match with hd800's. While waiting for an L-2 to pop up on the market, if you're at all tempted by the prospect of building a mainline, I'd highly recommend it. For reference, my listening impressions on the mainline -> hd800 pairing are in post #7 on this page: http://www.head-fi.org/t/683012/bottlehead-amplifier-discussion-comparison-thread-crack-sex-mainline