How much difference does a phono preamp really make?

I've got a Technics SL-1200G with a Clearaudio Charisma MM cartridge, and it sounds amazing through my Herron Audio tube phono-stage - yes, it can make an immense difference.

Last year I built a Pearl 2, a diy phono pre by Pass Labs designer Wayne  Colburn. At first I was disappointed. Things didn’t sound much different from the built-in phono input on my Rogue Sphinx 2. But keep listening. I realized the Rogue was very good, but also what I decided was merely “pleasant.” The Pass pre looked deeper into the music. The background was blacker, with less surface noise. So there were details coming through that weren’t immediately apparent. And that’s what you’re likely to experience, I would guess. To blather on, I think you’ll find something similar with cartridges. There are very good, relatively inexpensive carts like the Ortofon 2M Red and Blue or the AT95 family. Or the Denon, which I know only by reputation. Paired with a phono stage compatible with their signal output, they do a good job at a great price. I’m currently happy with a low-output (1 mV) Grado Opus3 MI cart through my Pearl 2 pre (55 dB gain in standard build). I plan to try an MC cart, but haven’t yet because I’m inclined to agree that it’s not worth buying a cheap MC cart. I’m sure I’ll spring for a good one when I’m feeling flush.

IMHO - the order of importance in SQ is arm (properly matched to a table), cartridge/phono stage (matched properly), turntable. Up until just last year, I didn't even know a phono stage outside of the one that came with my integrated amp (which is an excellent Plinius) could be a huge improvement. After all, it had a switch from MM to MC, and when I got a very nice van den Hul MC I switched it and it sounded fine. It didn't become apparent until I began contemplating a maintenance for the cartridge that a trusted dealer said to get an external phono stage before addressing the cartridge. What an improvement! (Only second to upgrading the arm the previous year). I previously thought the only people who needed a phono stage were those with preamps or integrated with no phono selection option, and for less expensive systems like mine was, it was right.

I also almost doubled my total stereo investment during that 2 year period (upgraded the table to match the arm, getting the Linear power supply for the phono stage, vibration control for the table). Everything does matter, and you want to fix the weakest link at any time, but sometimes that is not clearly evident, or maybe one part is more $$ than you want to spend at that time. If I did mine in a different order, it wouldn't have been a big deal as long as I got the proper part when I did it. So, if you do one before the other, it's not a big deal, but try to get a sufficient enough improvement so you don't have to upgrade that part again before getting to everything else you want to improve.

I like the arm and table from the same manufacturer or made for that table, a direct wire/cable from the cartridge output to the phono stage input to eliminate connector plugs, and integrated amps (less interconnect cables once again) versus separates. Also make sure the cartridge isn't too heavy or light for the arm.

So if you are hell bent on keeping that table (I like Regas for tables under $3000) get a cartridge and phono stage if you want to spend a couple thousand or more. If not, consider a new table first. It probably won't cost much if you trade your in (unlike cartridges which are worth very little used) and can last you a very long time.

I have not used a New Phonostage in my system that has not benefitted from a Extended Period of use.
Approximately 100 Hours of usage for a New Built Device seems to be  the point at which the Phonostage will come on song and appear to separate itself with a perception of a noticeable improvement from recollection of the previous time in use.

I personally feel even more time of usage will show a slightly more improved sound, maintaining a regualr use and keeping oneself familiar with the presentation, will be enough to reveal these later shift in noticeable changes to the Sound Quality.

If a Phonostage is heard as a New Phonostage and offers a impression that is a wanted experience, then the liklihood is that after a Period of usage the Good Impressions already made, will become even more substantial.

I am in a habit of inquiring how many Hours the Phonostage has been in use for when I discover a presentation that is to my preferences.

Something Similar happened during 2019/2020 with a Cartridge I had rebuilt.
It was initially compared with very few Hours of usage to Two other Cartridges from the same Brand in a friends System.
The Comparisons were able to be undertaken using the Same TT> Tonearm  > Head Shells.
The Two Cartridges had 100ish Hours and 300ish Hours of usage.
My Cartridge was brought back to be compared at approx' 50 Hours,
100 Hours, 200 Hours and 300 Hours.
At the visit with the 200 Hours of usage my Cartridge was very noticeably inproved during the comaparison and One Cartridge was sounding a Lesser Performing Cartridge and the other Cartridge, which was a Top of the Range from the Model Range during its time of production was being very closely matched in the Performances with my own Cartridge.

Both Cartridges have not changed in any noticeable measure since the 200 Hour usage comparison.

Maybe not in all cases, but it is worth inquiring about the Hours of usage when a Cartridge is being auditioned, as there will be a time when it is heard at it Prime, especially when the Cartridge has received a
100+ Hours of usage.