Since you say your wheels and tyres are new. There is a change you could have a distorted tyre. This can happen at manufacture. Usually difficult to balance but can balance out ok. I had a civic type r with a distorted tyre on the rear and at 75-80mph it sent a strange vibration through the car. One of the tell tale signs is the high speed than normal out of balance wheels which is usually between 55-65mph.

The other thing I can think of is that the allignment should be set after new arms and new wheel/tyre package. Also did the new wheels fit the hub centre perfectly? If they require spigot rings then you would know all about vibrations!