How would I even know where to look? It'd just be a random "try everything until you found something you like"-buy spree, which I can't afford. I wish there was a high end headphone/music store somewhere nearby, but I doubt there'd be more than one or two in the whole country. Everything is web shop nowadays.
Yep. Have you ever seen the trade forums on Head-fi? Or looked at user profiles where they list current and past headphones? Hearing different headphones is the only way to find that out.
You might look for a head-fi meetup in your area so that you could discover how more headphones sound.
I used to have the SR225i and bought them exactly for that reason. Best guess is that the difference between the 225 and the 325 is not in the drivers, but the plastic vs. metal cups. And I know enough about audio to know I didn't want metal creating reflections on the highs.