Kitch also knows about ITBs, saw his set up again at the weekend, very sexy.
Weber / Dellorto / Mikuni are best bang for bucks and best sound, but you will pay for it at the pump and in getting and keeping them tuned, but Oh that sound
Another option which is a bit cheaper and offers a power increase along with economy at the pump is GX 'SU' carbs, they can be tricky to tune too but usually once right stay good and economical, but they ain't got the sound but

SUs tend to start at $200, make sure you sort a choke cable also as they don't have an accelerator pump and don't like cold mornings. (Personal experience). SUs don't like huge cams either, so you can't extract the power you can from other side draughts.