Interesting! I haven't heard any tubes, so take this with a grain of salt. But my guess is that if you tried other pads (such as the HM5 hybrids) on the NH's, that you would greatly enjoy them on your tube amp.
Just curious: have you tried any other pads on the NH's? I didn't think I was ever going to do so, but did end up trying the HM5 hybrids (as per wuhanclan's suggestion), and I can't believe how much I am liking the sound. To me it's basically the same beautiful NH sound and signature, except with that bloom of which you speak cleared up. I'm looking forward now to trying the velour pads once they get here.
Yes, that's really annoying. I know you really like the 2D MSQD's ("those that shall only be named backwards" lol). How about everyone else? C'mon people, post your impressions (even if you have to do it in pig latin!). Anyway Eric, I'm looking forward to getting your D27 impressions one way or another!