You will not encounter a wheel too stiff for your frame.

I used to race a Specialized S-Works E5 aluminum frame with Mavic Ksyrium SL wheels. That E5 frame makes my current Caad-9 feel like a rubber band. And the Mavic's are a very harsh riding wheel - they transmit a lot of road vibration into the frame. Yet, I never had any problems doing short crits or long training rides - 65-70 miles - on that set up.