How much difference will a phono stage upgrade make?

For the past couple of years I’ve slowly been upgrading my audio equipment. I currently have a Primaluna Dialogue Premium HP integrated amplifier, an EAT C-Sharp TT with an Ortofon Quintet Black MC cartridge, and Tannoy Revolution XT 8F speakers. The weak link at this point, it would seem, is my phono stage, which is a Pro-Ject Tube Box DS. All things considered, my system sounds really good to my ears, but I can’t help but wonder what a phono stage upgrade would bring to the table. I’m looking at the Manley Chinook Special Edition MK II, which is a big step up in terms of cost, but I wonder how much better it will actually sound. Has anybody made a similar upgrade, and was there a marked uptick in sound quality?
I have both the Manley Chinook and the EAR 834P. FWIW, here are my impressions.
Both are excellent overall. I prefer the Chinook with MM cartridges, and the EAR with low output cartridges. Maybe it’s because the EAR has step ups for mc.  With the Chinook I alway use an outboard step-up for mc cartridges.
Back in the day I was blown away by the legendary Magnepan Tympani IVa , when the dealer insisted on showing me the ARC SP8 (phono/pre). The phono made more difference than the best speaker made !!! 

So yes - get the best phono you can stretch to afford and keep it forever. My opinion.
Regarding cwb3rd’s post about Keith Herron above: your customer service from Keith is not unique. I have experienced the same level of above-and-beyond service from him over the years. It started the very first day that I received the VTPH2 (now upgraded to 2A). It was 10 pm, I was trying to connect it to my integrated amp, and having problems. I emailed Keith, expecting to have to wait until at least the next day to get his reply and hear my new preamp. Moments later, he called me and very patiently helped me figure out the problem and walked me through the setup. That was just the first of many times he has provided similarly great service (and NO-that does not mean I’ve had problems with the VTPH, just that I have had many questions and requests as my other components and cartridges have changed, and I’ve upgraded it). This is just how Keith is. One of the true gentlemen (and most definitely a “scholar”—he knows his engineering and music) in the hi fi business.  To be clear: I don’t have any connection to him other than being a happy customer. The VTPH2A is a fantastic piece. I will never sell it! Best of luck to you.
Now, to answer your question, we could probably agree (or not) that Herron could be better in some systems, and Chinook in others.  But, the Herron costs double.  So, for me, moving up from $800 Jolida to $2500 (retail) Chinook, I don't see a reason to go up to almost $4k for the minimal difference in sound quality.  For another $1500, I'd expect to be blown away, and I

Thanks so much for that detailed input. My thoughts exactly in terms of the jump in price to the Herron. It gets to the heart of my original post—I want to be blown away if I’m spending this much money on a component. I’m feeling more confident now about making this purchase and what it will yield in terms of a step-up in sound quality. 
mmai -  Thanks so much for the info. I talked with Glenn at Aesthetix and he gave some tube ideas so I rolled out of the ElectroHarmonix and Sovteks. Ive got NOS Telefunken in the phono stage now. Lush sound, but alot of rush at my listening levels. But I have no point of reference. So your info is helpful. I could probably live with rush at the level you’re describing. For no particular reason, I haven’t tried Gold Lions but I definitely will. I’m all for a solution under $8,000 - so I can get that Lyra cartridge instead!!