Having owned all variations of the Extrema Ratio folders they get the nod from me.
I currently own none despite the fact that I like big tacticals and lock-backs because of their blade geometry. They are not going to excel at cutting which is 99.99% of the reason I carry a knife.
With your requirements I would go with any of the Extrema Ratio's
hands down.
From there, the sky's the limit.
The new benchmade Rukus is phenominal. Big beefy blade, good grind for cutting efficiency, best lock on the market.
Original Chinook, the biggest baddest Spyderco made, the Chinook II and Manix are along the same lines but not quite as beefy.
Strider AR/GB, liner lock's, but if you have to go liner lock this would be a good choice.
Severtech auto, an absolute tank with good cutting performance with an excellent lock (plunge lock).
After that, check out some of the amazing custom frame locks. RJ Martin would be one of my first choices. I also have one from Todd Begg that's phenominal but may be a bit out of your stated price range. The Carillo's are a cool design but his choice of hardware has never thrilled me. I have little doubt they would make excellent choices if a refined look is not high on your list of priorities.
From custom makers I would stick with frame locks. Unfortunately Axis lock's in a custom is almost unobtainable, and there are very few makers doing lockback's. Tab lock is supposed to be excellent but I have not had one, and liner locks are too hit or miss and just not as strong given your requirements.
Of course, as with anything these are opinions based on my experience and will differ from others. Unfortunately (or fortunately depending on how you look at it
) you almost need to buy a few and try them out, then either keep or get rid of the rest.
Best of luck.
How about a Spyderco Manix or a Chinook, with a replacement blade from 
