The V.P.180 is a little larger than the V.P.160. Though either of the speakers will be more than suited to the amp.
I'm running a V.P.160 through a ADA1250. Personally really enjoy the lower octaves the power can deliver, witch is probably more noticeable with the extra driver on the V.P.180.
The design of the V.P.160 is supposed to have the greatest off axis response with the drivers in that particular configuration. Where as the size of the V.P.180s configuration makes it just as capable with off axis response.
