not that you need it but semi pros set up it top notch, although as mentioned raid is a feature you cannot do without, so get the gigabyte or save up anoter £25 and get a asus p5k premium.
mobo stability isn't really an issue, and you only need to flash stuff when really new stuff comes out generally i.e. anything on sale today over £50 using commonly availible parts will have no issue.
all 3 boards mentioend are fine.