I've got a Nikon D70, first run, with an 18-70 f3.5-6.5 and 70-300 f3.5-6.5.

I do weddings and portraits and travel photography.

I am really frustrated with the D70's grain quality and lack of depth of field.

I am looking to upgrade.

So, Would I be better off with a new lens, like an 18-55 f2.8
or a D90, with my old lenses?

Thanks!