Yes, the GPU is definitely not an issue since I'm running headless most of the time. And the Pentium G620's GPU is so feeble anyway that you could probably run it on a x1 or x2 PCIe bus and not notice a difference.
I have not noticed any issues with CPU usage. It hovers well under 5% most of the time (it's almost embarrassing how over-spec'ed this box is with a G620, 4GB RAM, an SSD, and a server-grade NIC).
Actually, now that you mention it, I'm not sure if I'm running in AHCI mode or not. I'll have to check the BIOS settings. The dmesg log detects my SATA controller as:```
atapci0: <intel ata="" controller=""> port 0xf110-0xf117,0xf100-0xf103,0xf0f0-0xf0f7,0xf0e0-0xf0e3,0xf0d0-0xf0df,0xf0c0-0xf0cf irq 20 at device 31.2 on pci0</intel>