I'd have to agree about the Evox issues, while generally okay, there can be some head scratching issues that only the M8 bios seems to throw up. There is even a dangerous version that kills xbox's out there, hence why people dont outwardly mention this for fear of someone grabbing this bad version.
As the other posters state you'll always get mutiple answers from a quiestion like this, but so far as complete configuability is concerned the X2 5035 with it's x2config.ini (placed on E), is by far and away the easiest method, as you can use exactly the same BIOS and simply change a text file to get your changes, and yes this does Boot colours, LED stuff, fan speed, multi BIOS bootups, debug modes, XBL protection (i.e. it wont connect you) as well as other stuff.