The 2500/3000 spool size relationship is not exactly what it seems with Shimano. What determines casting distance (as long as you're talking about the same line and rod) is spool lip diameter, which is the same between the 2500 and 3000 size spools in the NASCI. So yes, the 3000 will hold more line, but the extra capacity won't be operationally available for the same casting distance as the first 75 or 80 yards. It's buried down in the line lay, due to a smaller-diameter arbor.
I got that information, BTW, off older specs from Shimano, from TW, and from sites like this: https://saltedangler.com/spinning-reels/shimano-nasci-reel-review/
There has been noise around that the relationship between the 2500 and 3000 size reels has changed. I don't know whether this is true or not. Whether the change involves a different spool size or not is unclear. Some sites list different weights, and some do not. It's confusing, to be sure.
One thing I do know is that Shimano makes slightly different models with slightly different specs for different parts of the world. With the internet making purchase from anywhere in the world a rather easy thing to do, I wonder whether some of the comments about changes in the NASCI lineup didn't involve some of these reels aimed at other markets.
Because you said that you fish rivers, I assumed (I know ... I should never assume) that casting distance was important to you. If you can examine a 3000 model, and if it has a larger diameter spool lip, and if the weight seems OK, then I'd say go for it.
Otherwise, my advice (to go to braid with a leader) still stands. It's not a perfect arrangement, but I think it will be a lot better than what you've got now.
Good luck! jj