Was gonna buy the tamron sp 90 next, then replace my 18-70mm with the 18-200mm VR but im wondering if I should just dump my 18-70mm now for the sigma 50-150mm f/2.8 since I've already got the tamron 17-50mm f/2.8 and the sigma can work as my macro lens temporarily. Or should I get the sigma 70-200mm f/2.8 instead of the 50-150mm? damn kau lots of choices out there  but I definitely will pick up the 90mm tamron later 

I'm contemplating whether the VR is needed since I've already got a monopod for the lens.

yeah I emailed sigma about it. The old version's chip is not compatible with D200 and they offered firmware upgrade for those lenses FOC....i asked them if all the new macro version comes with latest firmware.