I've used a M.R. RM5III for several years and have tried just about every 6dj8 and 6922 out there in the line stage except for really high priced things like pinch waisted amperexes. This sort of thing is dependent on your taste in audio, what I or someone else like might not reflect your preferences. That said, my favorites have been (in order) : Siemens 6dj8 from the sixties, 70's Amperex Orange Globes with halo getter, 70's Mullard 6922, and a very strange bird - a 6922 gold pin labeled "made in japan" branded "Ad Yu." I think it's actually relabled Apererex stock, looks identical to an Amperex in all respects. The "Rocket Logo" Russian 6h23 that Upscale Audio sells also sounds pretty darn fine IMHO, easy to get and not expensive. If you're lucky enough to find the 60's Siemens 6dj8 though, that one really is sweet. Holographic & liquid soundstage, good bass, airy treble.
