So much to look forward to: we've got Frank's review of the Mark III, and the Mark III itself. It seems like a lot of these tubes are pretty inexpensive while others are harder to find and more expensive. I'm most curious to see how much difference they make in sound. This could be lots of fun. As far as cans go, I'm pretty happy (really enthralled) w/my LCD's, but based on what I read of the Fostex's and the Senns, it doesn't sounds like you'd be unhappy either way, Landmantx.
They will be very noticeable on Decware amps. Do remember when you do roll leave tube you installed in a few day to see if you like the way the amp sounds with those tubes. Some people get neurotic and swap like crazy and never give themselves a chance ego see if they like the tube thats in there. usually when I find a combo I like I leave that in for sometimes months and then swap around again. There may be a eexceoption a ssome tubes you wont like right away and want them out but for most NOS European tubes they all sound very good with slight differences.