Glad to hear it. I'm upgrading my Apex 2 & Wise, and I can't decide between a Star 3, 4, or 5. Any thoughts?
Apex + Wise tension is alread a nice upgrade, and may be all you need. however, since you asked......................
The Star 3 and 4 both have identical moutning systems, clamp bases and center clamps. Where they differ is in the tensioning mechanism. The star 3 has a anaolog dial to set tension, and only pulls at one speed. That's it.
The star 4 is digital and has 3 different pull speeds; a "kevlar function" for strings that don't really stretch, cross button, tie of button, etc. So you get more bells and whistles. The 4 also has what is called a "load cell" to set tension, which is said to be more accurate than what the star 3 has. ( not sure if one is better than the other)
The star 4 is very hard to come by. I waited for over a year to find one. The star 3's are plentiful, and coudl be purchased at below 1,000.
the biggest selling point (for me) the star 5 has, is that it is new. I don't prefer the mounting space on the 5 over the 3 or 4, nor do I like the 3 teeth clamps that come with the 5. Also, the 5's base clamps is a round knob you have to turn to lock it in place. That said, it is still an awesome machine. However, if I had to go the route of a new machine, over a used one, for the price, I'd go with the new Prince machines. Not only are they roughly the same price as the star 5, but the mounting and clamping, IMO are better, and you get about $3,000 in strings.
Good luck!