This is an old thread you have tagged on to.
Homeplugs don't generally cause the buffering as they
can perform a lot faster than what your box requires.
Personally I use a set of BT 500Mbps and they are fine.
You would be best testing your internet speed, do an online test,
my mate had 8 Mb coming in and had lots of buffering on a Mag 256.
Same box and line at my house ran fine on 20Mb