Right now I have
2)KRK Rokit RP5's(originals)
1)KRK Rokit RP10S Sub

Now, My budget is around $1500, could go higher.
And though I love the sub...do you feel its necessary to have a subwoofer?

Do you prefer to have a sub? Is it necessary/recommended.
Do the major industry mixing facilities incorporate a subwoofer in the mixing monitoring chain?.

Genres. Rap/HipHop...R&B. Pop/Dance

Edit: Check this site.
http://www.independentrecording.net/irn/columns/gstep/index.php?id=82