the spyderco endura is awesome, and it definately offers a ton of cut for the money. At first i was put off by the lockback, but it really is easy to close one handed. Here is how, you slide the knife forward so the thumb is on the lock, and flick your wrist, this brings the unsharpened/unground "kick" of the blade down onto your index finger. (It is not too dificult to learn where your finger should be to not get cut) From there you can do alot of things. I pinch the handle between my thumb and fore finger. Then use my fingers on the spine, to close the blade. It sounds complex but it really is no tougher than a liner lock. At 3.0 ounces it easily meats your weight requirement. Packing 3 15/16" blade gives a ton of reach.
As for the axis, the grip is definately a nice knife. The spyderco will over better edge retention, and probably better ergonomics. But the grip has great ergos and the axis. So if you want to spend up, and are not too picky about steel, go for the grip 440c is plenty good. However dont discount spyderco, at 20 bucks cheeper they definatley offer bang for the buck, premium steel and great ergos. It weighs a bit more and is only 3.4 inches. Also is a little over your budget, but axis IS nice.
I have handled both of these knives, and I like both of them, although the endura seems to be a better cutter, the axis is definately fun.
If you dont mind SS handles, also check out the Cara Cara by Byrd Knives. They are spyderco designed and manufactured in china. They have either 440c or an alloy called 8Cr13MoV which basically is aus-8 according to spyderco. Definately the buy at 20 bucks but it will be a bit heavy at 5.625 oz but not too far away from that majic 5. It is just a little shorter than the endura at 3 7/8". I have handled other byrd knives and like them alot, although they might be a little stiff without militec or other luberication.
Now to look above your price range, the spyderco military is a nice 4 inch choice, but it is expensive at about $100. 4.2 ounces and definatley the toughest of any of the folders listed. Though the byrd is strong with SS handles, the military has better grip and more wear resistant steel. If you dislike the lockbacks, this has a liner lock.
Now, the endura fits your request perfectly. But consider some other things and try to make an informed decision. Any of these knives will suit your purposes well, and each has pros and cons, so figure out the money, the steel, the ergos and finally, choose based on which seems to fit YOU best, because compared to that, the rest of what we say is horse hockey.