sounds like you really want the Kefs. i dont know anything about them but the laws of physics can only be bent so much. the internal volume of the enclosure would worry me.
you have a big room that opens to another room so if you want room filling sound i dont know if these are the way to go. between the 2 you listed i would go for the Def Techs. but if it was me i would get front ported bookshelves and hang them. it does sound like you want a system that will hide in the room over sound quality.
another thing is those subs are not going to produce a lot of output in that large room.
so no i do not think in your room the Kefs are going to sound $1700 good.
only you can decide if the bookshelves would look too bulky on the wall. i put sound before looks so.....
in the end this is just my opinion, but again i dont think those will do well in your room, however if you want something better than your TV speakers most certainly they will sound better.
here is an example of some really nice looking front ported bookshelves that sound very good for the money.
and they have matching centers, but i have a feeling these are too big for you. they do also have wall mounts for them.Edited by mark62 - 1/13/14 at 12:39pm