Hi Michael,
I tried the Vengine 9 and found the lower tension and softer string made the racquet feel a little more cushy, but really did not improve the play of the frame too much. I still had trouble getting spin with the string pattern, unless I really followed through high on my swing. The grip still felt a little small even with a thick overgrip on, but not too bad.
I did have a blast trying the Diablo midsize! Wow, what a feeling! I could swing out on everything and the ball fell in the court. It was strung with a multi at 55 lbs. Very nice to hit with. Just had some trouble with returns, but I was a little slow also b/c of laziness.