I've only loaded my Deuter to about 30 pounds, but it carried it just fine. Also, on Backcountry Gear's website, it lists a 45 pound capacity for the ACT Zero 45+15SL. It's also about a pound a quarter lighter than your present pack.

I forgot to mention the Deuter ACT Lite series - same suspension as the ACT Zero, but with some additional features like a separate sleeping bag compartment with external access. Not quite as light, but still capable of 35 - 45 pounds, depending on the model you choose.

(In fairness, Deuter no longer lists carrying capacity on its website, so BCG may be estimating this based on last year's manufacturer specs, which did include that information.)

I've loaded a Kestrel 58 to 33 pounds and it carried OK (consistent with the Osprey website estimates), though not as well as the Deuter.