Unclear which version I should D/L...

[Phil]

My apologies for raising what must appear to be a very basic question, but I am attempting to crawl out of the clutches of Microsoft and have little to no experience outside of the Windows domain. 
Having carefully looked at the vast array of Linux and Unix distro’s available, I am keen to install FreeBSD on a Sun Microsystems box that I recently obtained through Ebay. The machine has dual x86 processors (AMD) and 32 Gb RAM. The boot disks are SCSI Ultra 320’s.
I have looked at your download mirror sites but am a little confused as to which version I should be getting.
Any help would greatly appreciated. Thank you.
Phil.