I'd go Hexagon at this point, esp Hexagon2; that is looking competative with Silo and possibly even Z-brush at this point. Carrara's modeler has the advantage of being simple and clear. If you see yourself getting better renders, creating scenes that can't be done easily in Poser (natural landscapes, trees, particle effects et al), and doing a bit of modeling it makes sense as one-stop-shopping. You don't really need a second program, at least not right off. I should caution, however, that the Mac version of Carrara5 is broken in a couple of small but critical areas when it comes to Poser-oriented modeling. I've had to shift the bulk of my work back to Carrara4.