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? 
@auxinput: thanks for the advice. SI and Stewart are both 1.3 gain however I've seen Stewart studiotek screen and it is way smoother than my SI. That's why I wanted to know if swapping screens would make a big difference. Ive also heard from 2 different resellers that upgrading screen is more important. Have you ever A B'd screens with same projector? 

@ricred1 What screen do you have ?

So screen quality does not matter as much as claimed by a couple of resellers of screens I spoke with !?

I actually have the Stewart Filmscreen StudioTek 130. It has a very very slight texture to the surface of the material. If your Screen Innovations surface is perfectly smooth, I can sort of see how you would think the Stewart "looks" smoother on video. I think the texture on the surface acts to break-up the separation between pixels - as the LCD pixels do not have a great fill factor. If you look closer, you might get a "screen door" affect where you can see the pixel grid. If you wanted to smooth out the effect of your current Epson LCD, the Stewart -MIGHT- help fix some of that pixelization roughness. I don’t know for sure. You can also solve for this by very slightly de-focusing the image so that the pixels sort of flow into each other.

The JVC DLA and Sony LCOS panels have a much better fill factor - you will get less of the screen door effect. I have an older Sony VW95ES 1080p that I just love. To this day, I have not had any urge to replace that projector. Though, it does have a color calibration using Lumagen Radiance processor. If you’re not worried about 4K output, Curt Palme website is selling the Radiance 2020 for $1399.

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.