Here's what you can do

First, go to ASUS website and download the lastest BIOS, then updated your motherboard with it. It is a risky operation so read instructions very carefully before you doing that. After you finish this, get into BIOS and "Load Default Setting".

Then, use BIOS to check the VCore. Yes VCore is cpu core voltage. Their should be a menu like "PC Health Status" you can use to check. Refer the manual to find it. The VCore should be no more than 1.5V.

If it is still 2.5V, you better contact ASUS support to submit this question.

Regarding FAN noise, my PC has a Intel 3.0 HT 1M cache installed too. Same fan from Intel. Noise is low because it works at 2000 rpm when idle. The fan speed should be controlled by motherboard automatically and it rises when CPU temperature does. So make sure you connect the fan to the right connector (the one marks with "CPU Fan"). BTW, my motherboard is from MSI.