Can you recommend some very high quality hex wrenchs?

Several brands to choose from. You want ones that are HSS (high speed steel) or tool steel. they won’t round off the tip or out the inside of the screw. I sold and used this type of tool for many years. As BH stated MIP are excellent. 
My personal preference are the Hudy brand with the resin handles. They are same tip as the Hudy aluminum models but less expensive. And a bonus is, if you ever did need to replace the tip, you can buy it without the handle. 


 

I was just about to ask about MIP. Thanks.

I think theyre way different price ranges, good consumer brand is Bondus. Great fit and dont damage fasteners. 

Pro grade would be Wiha, Klein, MIP etc. If you have the money to spend get the German stuff.

I am really looking for pro grade - enough with the consumer hex wrenches. It's not that I want to spend a lot on tools, but at this point I've gone through so many hex sets that I think I need the next level of performance. I've probably paid for the pro stuff with multiple lower level purchases.
 
Several brands to choose from. You want ones that are HSS (high speed steel) or tool steel. they won’t round off the tip or out the inside of the screw. I sold and used this type of tool for many years. As BH stated MIP are excellent. 
My personal preference are the Hudy brand with the resin handles. They are same tip as the Hudy aluminum models but less expensive. And a bonus is, if you ever did need to replace the tip, you can buy it without the handle. 


And..... I was just about to ask about Hudy. I remember them from Team XRay and RC days. They make some serious quality stuff with a special spring steel IIRC. I don't know if I can swing that - an 8 piece drive set is $150. Yikes!
 
Many great name brand hex tools have been mentioned here, and it was not long ago I was in search of such quaility hex tools myself. Regardless of name brand hex wrench tools you chose I would highly recommend that an anti-seize compound be used on the screws/bolts, its cheap insurance that helps prevent stripping and breakage of fasteners - not to mention alleviating the frustration level. Having two different metals overly torqued together in time often tends to have a welding effect of some kind and the simple application of anti-seize has prevented me much frustration as noted.

I have even purchased better grade bolts to replace what I felt were too soft of bolts for said uses, again I considered this cheap insurance. 

Just my 2 cents
 
https://www.homedepot.com/p/Husky-SAE-Metric-Non-Slip-Hex-Key-Set-18-Piece-HNSHKSM18PC/204761077

I’ve posted these up on every Allen wrench topic ever brought up. I keep a set of these on hand, for the minute I feel either my wrench got rounded off or the actual socket of the fastener is feeling rounded. It’s always on the smaller Allen bolts, like the four holding down the breech block onto the air tube on a Marauder rifle. 

The tips of these wrenches have exposed “teeth” on the sides to “bite” onto the corners inside the four sided Allen socket. I only use them as an emergency, and not as a sole Allen set for everyday use, cause they can start mangling the inner corners of an Allen bolt with repeated use. Only for emergencies.