i played the n6.1 95 (18x20) for a year before moving on to the nblade 106. the n6.1 95 is rather heavy, so probably you got the pain since you were at a point starting to hit late, thus putting more stress to your joints than the heavy racquet itself generated anyway.
i didn't hit with the pure storm and the k95 at all, so there's nothing i can say about them. the pure storm though seems to have a lot of followers on this forum, and whatever people may say about the pure drive, i see quite a lot of players using it with good results, not only speed/power-wise but also touchwise (playing dropshots and other touch-strokes). i couldn't make friends with it, but i think that it was rather due to the fact that i'm playing eastern grips, so i coudn't really tame it's power.
what it all comes down to, and here i absolutely tune in with the other competent posters, is what the racquets do to your game! so best thing would be to demo and thus make a practical approach decision. what works for me perfectly well could be the perfect disaster for you. the racquets you have chosen are all good, but have their own characteristics and balances of power, touch, control, spin potential, which in the end have to support your game. you should rather not adapt your game to the racquet but adapt the racquet to your game - if i would have gone to semi-western or western grips, i most probably would have found my way with the pure drive, but it was easier and more rewarding for me to stick with the n6.1 95 at that time, because i could just build up on my game instead of turning everything upside-down.