Here's the frequency chart for my SE425X3 (remolded Shure SE425 with added bass driver).
So, as you can see the bass is very much more prominent and deep than of a stock SE425 and that was exactly what i had hoped for, all the high end definition of the SE425 with added low end punch.
The sound is very well balanced to my taste, bass is nice and punchy and the highs are nice and crisp, but not sibilant at all. There could be just a little more mids, though but it does not bother me as it is. Overall I was surprised, what a huge improvement this remold+upgrade was. i would suggest it to all who own se425's and wish to have more bass (not to mention perfect fit). =)