This was the main reason I liked the 325is over the MS2i…the bass.
I think the 325is is just fine stock. I tried the vent mod with my first pair of 80i's (2) holes, and hated them, they lost their excitement IMO. So I tried to fill the holes with hot glue (stupid move), and it dripped onto the drivers, and that was the end of them! So I immediately bought another pair and put the Vibro Labs "classic" wood cups on them and (L) cushions, and they sound/look beautiful.