???????
I don't have the vibrator you mention, but when i watched the video on redtube recommended in the thread, "i know this guy..." i saw another with a guy using a Peridise with a vibrating bullet inserted at the same time. I tried it and found it perhaps added something to the Peridise, although alone it is more than enough for me. My fear of using a bullet is that the wire might break off and leave the bullet inside. If i couldn't get it out, even by pooping it out, it could be an embarrassing moment with the doctor or ER. Your vibrator is external so not that problem. The Vice has a vibrator inserted, which never did much for me, not even as much as the bullet.
I've used a vibrator, not the Hitachi, in sessions with my helix syn and progasm ice with great results. Holding it against the base always gets me to the edge. I try to not use it during my Super O. Really feels good to my prostate!