Re: Any sage VXP users here?
I use SA GPX Textured WF7 on my 7100-4 VXP. I chose this line because I'm generally fishing very close, and nymphing 90% of the time. The other 10% is streamer fishing.
I fished a guides 590 for an extended period and honestly don't know what line he had it paired with. In my opinion, however, the VXP 590 shouldn't need a heavy line and I certainly wouldn't consider going up a full line weight. Based on what you're doing with the rod, which is an all around rod, streamers, nymphs, dries, wets, I would look hard at Rio Gold. You can still find some of it on sale for around $50 because they changed it some (another topic in this forum somewhere - but I've not noticed a difference and I own old/new). Another line I'd consider is the Airflo Tactical WF5 (not Airflo Technical, more of a specialty taper).
As a side note, I'm surprised to hear about your experience with GPX line. I fish a lot of this line in various line weights. I've never had a single issue with SA GPX line, either textured or standard.
Good luck, I've found experimenting with a lot of different lines has helped me dial in my rods. It has been a rewarding part of my flyfishing education as I finally nail down the right taper for the right rod for the right situation. I'd look hard at a true 5 weight line on your VXP 590.