Top end response will be more extended, but I think the most noticeable improvement is the very flat, extended bass response. The stock head has a bump in the bass response - IIRC around 90Hz - and is down a little bit by 30Hz. These deviations go away with the extended response head. The output of the extended response head is a bit lower than the stock head. In practice this is usually not an issue with the Eros, which has plenty of gain.