And, relax.
Well, I've had the new curvy SCM40s in my house now for just over a week, and have spent hours in their company, more than enough to have really got under their skin so to speak, and find out if it's a love affair that has the staying power. I have concluded, that in the style of a good red, the more you drink of it, the more sublime it becomes, so for me the journey over for time being, this combination of Norwegian electrons and Gloucestershire prize fighter has me absolutely enthralled. I've no idea what the old tweeter was like, but the new one is something else. All of the reviews keep adding caveats about ruthlessly revealing poor recordings, almost suggesting that some of your music collection will be consigned to to the bin as unlistenable, well they're not. It's not a good description of what is really going on; I understand the comments, but it's been poorly explained. Everything sounds good, just that some recordings are excellent, truly excellent, and that you will more easily notice the difference between the two extremes. That is not the same as being unlistenable, harsh, lacking detail/musicality or whatever other audiophile adjective you care to apply.
In practice, cymbals sounds like cymbals; loud, crashy and metallic, that metallic shimmer they seem to possess. They might not have the most extended bass, but it's all there, where it should be and not smearing vocals, or hiding lower mid detail. It's possible of course that an underpowered inferior amp would render them a lot more difficult to listen to, but the combination of the Heg and the ATCs is fabulous, at any volume. Films are a revelation also, I watched Top Gun (as you do) last night on Blu ray, and whilst unsurprisingly the sound of F14s blatting across the sky is something special, it was the musical score that I noticed had changed! Kenny Loggins has never sounded so great, it absolutely thumped out the soundtrack, just like it was supposed to with the subtlety of a jet fighter smashing you between the eyes!
Have to say thanks Rick for helping me out!