Try the Spyderco Manix 2.
The Ball lock is as sturdy as they come, and the ergonomics are sweet.
It is a little over the $70 limit ($82 most places), but you'd be getting one of the best knives out there for the money.
If you can find an old D'Allara drop point those were usually around $60 and feel very good in the hand, it's a very good utility oriented knife. The biggest complaint most people have with the D'Allara is the large handle.
If you want an AO from Kershaw the Spec Bump would be good. The blade steel won't hold an edge like 154CM but it's one of the best AO's on the market.