Good choice on the racquet!
I have been using several different strings in the APD. My favorite right now would probably be Volkl Cyclone - that's one of my favorite polys right now. I also been playing with the Luxilon 4G for a little, but I do get a sore elbow from that (and I have pretty sturdy arms when it comes to stiffness), so while I wouldn't necessarily recommend it to someone with arm issues, I did enjoy the lively feel and the ability to really rip the ball. To be completely honest with you, I enjoy playing with the racquet so much I haven't quite whittled down what string I would choose over others specifically for that racquet, because I'm happy to play with most polys in there.
Polyfibre TCS is actually a good choice - in comparison to something I have been using like Babolat Pro Hurricane or Volkl Cyclone, it will be softer (better for your elbow) and more powerful, like you are looking for.
I talked to our string expert Jon, and he also suggested Dunlop Black Widow, or Tourna Big Hitter Black for more comfortable, yet powerful polyester strings.
Let me know how TCS goes for you.