I personally like the intel onboard gfx. You can run the cpu without additional gfx card and have got vaapi video accelleration. The main reason to get Xeon is usally to get ECC RAM support (that required the use of a workstation chipset like C206 but with bios update). If you want to max out the chip with oc you would be better with a K cpu. If you dont need ECC support then any s1155 board should do that has got ivb support. As you do not own a snb cpu i would not recomment to buy a series 6 board as you at least need a bios update for ivb. What i do not get is that there is no new Panter Point workstation chipset, the C206 is still Cougar Point (series 6). If you want ivb get a series 7 board, like something with z77 chipset.
If you really use/test uefi features it is definitely possible that your board will not post anymore. As the config is not stored in cmos you have to replace the eeprom. So best would be get 2 boards for hotswap and of course something with flashrom support Or get a board where uefi is known to be stable (i dont have got so many retail boards, just 1). I played a bit with uefi boot entries and changed bootorder in uefi setup and got a nice vga led only with my asus p8z68-v. dmidecode thinks the bios vendor is AMI, but i dont think thats fully correct. Looks more like Insyde. mac address is stored at offset $1000 for the single nic on it.
I can not recommend any vendor as i don't have got the big comparision. Since series 7 even gigabyte has got uefi (series 6 had got bios with uefi addon), but i don't know if gigabyte fixed the usb booting problems with hybrid usb sticks. that means avoid gigabyte series 6 at least. asrock seem to work with usb keys and has at least beta updates for ivb and older systems. msi well disappointed me with the bad bios update support for series 6 boards. only for boards you could not buy before ivb launch you get ivb bios updates or maybe i read their support page wrong - did you see a bios for a h61 b3 marked (not g3) board with ivb support? so i would not expect many improvements in the future. so choose your poison
Btw. the asus p8z68-v did not init the onboard gfx of a xeon test chip, so asus does not really like those cpus, you can be sure if something is non standard it does not run. At least i would not recommend it for a Xeon if you want to use the gpu. Basically there is absolutely no technical aspect against running xeon chips on consumer chipsets. The ecc thing is just a marketing issue nothing else. At least asus has a gui tool for modifing the startup logo - but only on win.