Normally, I'd recommend the A/V-3's for larger spaces and nowadays, the NEO-2X for smaller spaces. I've built and listened to both. Even though your sister's listening space is smallish, since it opens into a bigger volume space, overall, it's a big enough total volume to really benefit from the A/V-3's. You could also use my cabinet design (the RAV-6 in the NEO-2X thread) and build a tower version of the NEO-2X. That M-165X is quite a nice mid-woof, and if your sister appreciates the best highs (cymbal shimmer, etc), the planar magnetic tweeter in the NEO is very nice.