Selling because I've come to realize a Mac will fit my needs better :S
Not gonna win a lot fans with this statement. lol, jk. And Holy jumbled cable mess batman!
First off, you need to learn how to properly sell stuff on ebay. There's lots of tutorials and guides, even directly from ebay themselves. The biggest thing that is hindering your listing is the very generic title. "Server/PC with high end graphics card" is not going to win the hearts and minds of people looking in this category and again, your jumbled cabled interior "glamour" shot of the PC is not going to win any beauty awards, specially if that's your only photo/display photo when being listed.
Put up descriptions about the parts in your title, you have lots of characters to use in you title, more if you opt to buy a sub title. Post that its a dual cpu opteron 6128 workstation and that it has 12gb of ddr3 1333 ram with a 5870 6 eyefinity card. Look how other people are setting up their PC selling tabs and you can always google for free ebay templates.
Even though you got some decent parts in this rig, I highly doubt you will find anyone willing to spend more than 1300 for it used. My advice is to part it out. As a workstation, some of the components seem lack luster while others you just went balls out for no reason. You don't need a 1200w Antec PSU that' rated to power three 580's in this PC.
The 5870 6 eyefinity gaming, while a great card, is also a mixed choice as a workstation card unless you need 6 displays off of one card; personally nvidia cards are usually better tasked since they have CUDA, but even then, I would have paired this system with a proper workstation card like Firepro or quadro, but it still depends on the applications you were using this rig for.
12GB may seem like a lot in gaming computers, but for workstations, that's crazy low. The mobo you selected caps at 256GB so why not even put 32GB in this system if you were willing to pay $400+ for the mobo and $200+ per cpu?
And do you not have normal hard drives in this? You only have an old 32GB ssd listed.