My 2 cents:
I'd just keep what you've got and really save and then invest in something very high end down the road if it is something you REALLY want to do. I don't see how either the Prince Neos 1000/1500 or Gamma 6004 is going to be a giant upgrade to what you have; 360 degree rotation, 6 point mount, and a Wise.
I'm not the stringing/stringer expert these guys are. I have strung on only glide bar machines; Ektelon H, Neos 1000, and Prince P200. For me, the constant pull of the pneumatic P200 made it the fastest and most accurate in my learning stages of stringing. If I were to upgrade, I'd have to go to swivel clamps for fan patterns, ATW w/o adaptations, and just go BIG because the pneumatic pull is fantastic and very reliable. I'd like to stick with the 2 point or 4 point mounting for what seems to me to be less obstruction when I do small racquet heads such as badminton. Like another poster said, I would also consider an automatic drop weight such as a Stringway too.
Back to using POGs. Why did I ever leave you dear friend?