the reason i suggest p45 is it appears the op wants this for quite some time. may not plan on crossfire. but if down the road a year or 2 or even longer, lots of people keep rigs for a long time. it may be very cheap to add another of the same card and get enough performance without having to spend the $ on a new single card. but if that never happens and crossfire was never used you aren't out the extra money an x48 would have cost you. so to me it is sort of taking the middle of the road.
but i do agree. if no crossfire at all the p43 would be the way to go.