I just installed El Capitan on my old GA-EP45T-UD3LR, Wolfdale E8500 build -everything seems to be working perfectly (except for audio).
I'm also using Clover for the first time - which is probably why I'm having no luck with my ALC888 audio. I used Chameleon/Chimera & Mulitbeast for 10.8, 10.9, & 10.10, and had no issues finding the right kext to use, but with 10.11 and Clover, I've tried every method out there with no luck. At the moment I'm using Syba USB audio device, $7 off Amazon:
http://www.amazon.com/Syba-SD-CM-UAUD-Adapter-C-Media-Chipset/dp/B001MSS6CS
And I will be using this until I can find a solution to the on-board ALC888 audio for my board.
Everything else, including sleep/power off, my SSD RAID, dual monitors, drive recognition, USB ports, etc. seems to be working just fine.
I'm amazed at this mobo and CPU btw... It has been so good to me over the last 6 years. It seems just as fast, if not faster than other retail macs I've used recently - and I tend to push it hard.