The NUC has already been replaced as the first one had a damaged antenna wire. I think it's just the placement of the antennas within the box. If I re-orient the box, sitting it vertical with the top facing the router (which is about 40 feet away (and 2 walls), speed goes up to 245 Mbps.
I have ordered a pair of external antennas to mount on the box and that should do the trick. I just need to figure out how to mount them without causing conflicts with anything else in the box (space wise)
http://www.amazon.com/dp/B00DP64JRG/ref=pe_385040_30332190_TE_3p_dp_1