I like them with WA2 and warm 6AS7 clear top+ Valvo d-getter e88CC and RFT EZ80. Personally I've already expressed my findings here:
http://www.head-fi.org/forum/thread/494487/another-wa2-tube-roling-thread-my-findings-after-couple-months
Oh and I like WA2 combo better than HA5000, at least most of the time. The key to the sublime sound of W5000 is the source - analog like and a bit warm ,amplification and fit - I've inserted a bit of climbing rope inside - the same as rubber tube mod but slightly different properties - it will behave similar to integral part of the pads but create kind of resonating cavity so my ears are going inside pads not on top of them. this will help also with any fit issues as there is better fit and more presure applied by the pads also your ears are in slightly different position and distance from drivers than normally. To me this mod, totally reversible BTW, adds a bit of body and intensity to the sound. Rope color is a bit extreme but I'm looking for black of the same size - diameter is important as you do not want to create too much space inside the pads. This mod is nothing new and credit goes to whoever invented it. I just modified this with rope as rubber tube was not working very well for me for some reason.
See pic , hope this will help somebody.

Edited by Aethelred - 6/27/11 at 2:05pm