Cat6 is a lot easier to terminate than Cat6a, if you're going to buy shielded cable and then just ignore the shielding you could possibly end up with poorer performance than Cat6.
If you're doing overkill for the future then pull in 20mm flexible conduit so you can just replace the cables in the future if something else comes along.
In order of things I'd rather do to get cables in (ignoring surface runs or just kicking things under carpets):
- Not do it at all
- Fish down existing capping from loft into an existing box (maybe pulling out a useless telephone cable at the same time), this is very dependent on how your house was constructed as some cables will be clipped and then just plastered in. Obviously this only works if the capping has low voltage cabling in already - e.g. you can convert a TV outlet into a TV and network, but you can't have mains power in the same box
- Drill into the top of a stud wall and drop a cable down from a loft, cutting a section of plasterboard out to get past a noggin (if the wall is timber, if it's a really new build it might be metal framing)
- Lift carpet to get into a floor to come up or down into a stud wall
- Drill through an external wall to route cables between floors on the outside of a building, hiding conduits behind downpipes where possible
- Cut a plasterboard ceiling open to run cables up into a stud wall
- Chase cables into solid walls and redecorate
- Lift up a tile, lino or wood floor to run cables up or down into a stud wall