The first thing you need to do is check if its the VIVO version. This, I have read, is the only version of the X800P that you can flash to X800XT PE. The non-VIVO version, I believe, is somehow "locked" so you can't do it.
Also, don't just jump into a BIOS flash. Just because Jo-Blo can do it on some random forum, doesn't mean that you'll be able to. You should first try to get to XT-PE speeds with simple overclocking, and also trying to unlock the extra 4 pipes (assuming you have a VIVO card, otherwise, this is all moot). If you can't get it to XT-PE speeds, you may just have a card that simply can't do it. Then again, you may have a card that will go further than a XT-PE. If so, great. Just make sure everything is kosher before making a big move like flashing the BIOS and then rendering your card merely useful for a necklace.
OT: Yes, you'll probably be OK with those BIOSes. Just make sure all is good before you do it!