I'm using a Tyan S2885, which appears somewhat similar to this.
FreeBSD has run flawlessly for me - no reboots, crashes or
other headaches. I'm using FreeBSD 5.2 RC2.
The onboard sATA on the S2885 isn't supported. The GX28
uses a Promise controller chip that is more likely to work.
I have no idea if the LSI SCSI controller is supported.
It's a BCM5704c ethernet: mine is a 5705.
I'm using 8 GB of memory (8x Crucial part #CT12872Y335)
and a HighPoint 1542 sATA controller.