How much difference does a phono preamp really make?

Assuming your cartridge is decent enough, I would get a well reviewed and revered phono stage that’s within your budget that allows that cartridge to be all it can be. If at that time you sense that it could be better, upgrade your cartridge. Since owning turntables and associated gear since the 70s, I’ve adapted the ability to tell if the cartridge is the limiting factor vs the phono stage and vice versa.

Get the pro-ject tube box ds2...it has an abundance of settings right there on the front panel for both mc and mm...in addition, you can run 2 turntables at a time. It has received numerous positive, some glowing, reviews and it has tubes, 12ax7's....

“Get the pro-ject tube box ds2...it has an abundance of settings right there on the front panel for both mc and mm...in addition, you can run 2 turntables at a time. It has received numerous positive, some glowing, reviews and it has tubes, 12ax7's”

The ds2 tube phono preamp is a great value and sounds great with the right tubes, although stock tubes aren’t too bad. After much tube rolling, the Baldwin(Raytheon) 1960 or 1961 yellow labeled, black plate tubes were far and away the best sounding tubes in that phono pre. I tried 1959 Baldwins in the DS2 and they sounded excellent too, but the 1960/61 tubes had a slightly better sound overall.
I now have the EAT Petit phono preamp and it’s even better ( less grain, a touch more tonality)but the 1960 Baldwins weren’t great in it. The 1959 versions are fantastic in it and it now easily competes with my Modwright PH9.0X phono pre and that’s saying a lot! 

I did not notice much difference between phono preamps and cartridges until I had much better amp, preamp, and speakers. 

So, cartridge is important, phono preamp is important, as many people said, but if the rest are not as revealing, upgrading cartridge or phono preamp won't do much improvement to the overall sound.

The front end of the system is where you really have to get things right. It makes no difference how good your amps and speakers are, if the phono section isn't right (along with the turntable/cartridge itself) there's no way you can make up for that downstream.