Just arrived, new GM Deluxe 40, may be short lived if I can't work through the high end harshness issues...

Disappointed with my new GM 40 tones. There's a harshness to the upper strings (higher freqs.) that I can't seem to dial out. There is good clarity and tightness on the lower strings but I basically have to put trebble at 0-10% and the presence rolled all the way off to keep the chain saw in my ears effect to a minimum. It's generally more pronounced with boost on. I'm getting this even with gain on Crunch and Lead channels @ ~3 o'clock. For some reason it isn't quite as noticeable in the Ultra channel but I think that is voiced a little darker ala the "American/Mesa" motif. Is this to be expected? I did see the other threads dealing with this (not until I had ordered it unfortunately) and don't hold out much hope for a tube swap changing this. For this kind of money I need to be in "love" with this amp but I'm not there. As a side note these buggers run pretty warm to the touch. Any comments or advice would be appreciated.

The heat issue is not worth even thinking about.  They run hot to the touch because the metal cases are acting as they are designed, drawing the heat out of the inner workings to the outside air.  Way back in my younger H&K days we did fairly extensive work on this even going to the extent of checking this out with an infra red thermometer gun.  The temperatures inside the upper valve case are just as any other amp, the temperatures in the lower casing are lower.  There is nothing nicer that an insulating wooden box to let things get hot inside an amp!  Trust the H&K designers, this is an area where they have done lots of sums and their homework came in at A-10/10.

Regarding the high end roughness.  This is something that I personally have suffered from in my own TM36 and GM36 days.  The only thing I ever found to tame it somewhat was speaker selection.  As you will have seen, having browsed the other threads, I am a firm non-believer in valve choice being significant.  I'm an electronics design engineer and live with components every day.  I understand their specification and use and I know how little difference there is even before they are put in circuits which are designed to minimise any differences anyway.  What most people experience as differences in valve makes usually comes about by waiting until they need a valve change, going for a different make, finding their amp sounds different, then they claim it is because of the make of valve they have put in.  They completely disregard the fact that they have taken out an old faded set and replaced them with a new set which is what causes the difference.  I won't bore you with a complete diatribe on this as I can do but if the proof of the pudding factually is of interest to you then go to my post here if you haven't already found it:  Debunking Valve Type Differences

What speakers are you using the GM40 with?  Getting to grips with that will make a much more significant difference than any valve change will.  Loading on your guitar can make a difference too.  You could simply try using a longer lead or adding a touch of capacitance to the guitar output to drop its high end resonance.  That can make a useful difference too.