If they're for music they won't really cut the mustard. A sub/sat system will be hard pushed to perform well with music. There are also several different Kef Egg speakers- which one are you looking at? And Bose don't really offer VFM.
But it depends how fussy you are (I am) and what your budget is. I've listened to Kef and I wouldn't give them space in my house but listen to a range of speakers from full size/ full range to sub/ sat systems and decide what meets your needs best.
The sub is perhaps the most important part of a sub/ sat system (and an AV system) and there is far better out there than Kef.