I think you have the gist of it from the other replies. J011y has the most experience with kevlar of the players that I know.
I've played the 60# Ashaway/Alu combo and it was fun while it lasted. He's right with the tension on the kevlar but what he didn't mention is that it is assuming that your arm can hold up to it. J plays with a 14+oz? frame with silicone which mitigates a lot of the impact. In a regular frame, a setup that high will feel like a board. You have to swing the crap out of the frame to get the strings to bend.
Currently I'm experimenting with Wilson Hyperlast mains (A smooth Aramid blend) and poly crosses at #48. The feel is solid and the control is nice but you won't find that extra power you're craving. You'll have to supply it yourself! As was mentioned above, there are always tradeoffs with everything.
If you don't have issues with durability, drop the gauge of the kevlar a bit. Two strings I'd give a shot are PolyStar Energy-- rather lively but soft, and Adrenaline-- it's the faux Alu that won't hurt your wallet. (If you have the budget, go for the full Alu.) Between these two you'll get a full spectrum.
"Play like to want to win, not like you want to avoid losing."