Upgrade the projector or projector screen?

Hello Everyone!
 My Current setup: 
Epson 5030ub + Screen Innovations series 3 - solar white (1.3 gain) 100 inch diagonal.

I sit about 8 feet away from the screen and my HT setup is totally dark with grey walls. 

My goal is to upgrade the picture quality and I want to stay under or around $5k. 

My QUESTION: Should I upgrade to a Stewart Filmscreen StudioTek130 screen OR upgrade my Projector to a JVC DLA x790r or similar? 

What will make the biggest positive impact? 
My 13 year old son said he could see the pixels when we had the Epson 5030, but the picture is noticeably sharper with the 6040.
@ricred1 thanks for your feedback! To my eyes 6040 is slightly better but not by a huge margin. 

I'll be switching to a JVC x790r. Let me know if anyone is interested in an Epson 5030ub. It has about 188 hours comes with extra bulb (new) box manual remote and 3d glasses 
Last question:
Going to a JVC x790r from Epson 5030ub. Is that a significant of an upgrade? 

I think your screen is very good and your projector is too.  If you really want to upgrade now, then the projector will make the biggest impact.  if you had room lighting or a very crappy screen now, i can see how a better screen would make sense.  personally Id wait a year to make a bigger jump but either the sony or the jvc 4k projectors will be a decent upgrade if your sources are hdr.

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