Your subject line says VirtualBox 6.1, but your text says 6.0...
I run FreeBSD 13.1 currently under VirtualBox 6.1 under Windows 8.1, and have used VirtualBox for Windows virtualisation on my Ultrabook for many years. This FreeBSD system has 2048 MB memory allocated.
You need to tell us a lot more about the "Memory error" before any sensible comment can be made.
I see from the spec sheet that the Proliant G9 E5-V3 has an external connector for a
HP c-Class Blade SUV (dual USB3, Serial, and VGA) cable.
I would examine the BIOS to see what the boot options are. In particular, can it boot from USB drives? If so, I would test to see if it could boot from a thumb drive on a USB3 hub. That way you could test FreeBSD without disturbing the existing system (you would need the hub to connect keyboard, mouse, and USB drive).
The tech specs are a little vague on the SATA disk controller. It would need to be looked at (
JBOD mode is best).