http://www.evga.com/thermalmod/ Pretty sure the increase will only be in the vicinity of 400rpm, certainly nothing you will notice. It will still be a quiet card under load.
What's it matter anyways, you said yourself that you're using a customer fan curve so the bios changes are irrelevant to you.
On one hand you're saying a fan speed increase is pathetic and ridiculous, yet on the other hand you're using a custom profile. Bit contradictive?