With those high speeds you'vegot to give up something. If you want 340 fps with a 7.5 inch brace height, you'll be shooting a bow with a VERY aggressive draw force curve and basically no valley. UNLESS they made a technological breakthrough that allows them to push the bows efficiency into the 90-95% range.

Go to Huntersfriend.com and read the article about the 400 fps bow. It does a real good job explaining the theoretical limits of bow speed and the tradeoffs that go into getting those high speeds. It's all about the draw force curve and efficiency.

http://www.huntersfriend.com/bow-review-400-fps-bow/400-fps-compound-bow.htm