Just follow the cryptobadger post to a T when editing your own BIOS, it's easy as cake.
The thing about Trixx is you have to reapply everything everytime you reboot. Afterburner doesn't change the voltage on the new cards, at least the last version I tried. cgminer may or may not in windows, but the values are usually off, it won't control voltage in linux. sgminer miner though, you might have the best luck with for controlling voltage in the prog.
Ive been following the cryptobadger guide, but when i got to look at my card for the BIOS switch its not a switch so much as a logo button. According to the sapphire page, its has a legacy bios and a UEFI bios, so would i b overwriting one of those? it looks like this
http://prntscr.com/2subd6
I've never changed a BIOS like this before, some settings on a motherboard on pc load up sure, but not this. I've got the changed .rom files on my MSDOS usb drive ready, I just didn't want to screw it up. I've also played around with the settings a bit and still can't get my cards to not go over 80C
http://prntscr.com/2sudkz
R -> L card 1 is usually ok temp wise cards 2 and 3 are obviously too close. and always go over 85C what ever the settings I've used so far.
As for hash speed best I've seen was around 650 per card, lowering the VDDC via trixx to 1100 didnt' make a difference and the more i look at cgminer settings the more suggestions i see :S so not sure where i'm going now. A guide i read said it could get annoying and frustrating... no kidding!!