HI, I'm looking for powerful,very stiff,head heavy rackets from the big three companies. I'm an intermediate player, Aggressive smasher type,good at defending. I play singles and play twice a week. My current racket is a Nanospeed 9900. I'm looking for a more powerful racket than this. I also want a racket that is very durable. I'm thinking voltric zf/n90/sw35/voltric 80. Any opinions on these ?