Ive been doing a lot of research lately and I still don't know what piece of gear I want to get next. Right now I own a Nikon D40 body, 55-200mm VR lens and the 18-55mm kit lens I got with the D40. Originally I was planning on buying the sigma 70-200mm f/2.8 but that is a pretty expensive lens and my 55-200mm has been suiting me pretty well. I want to replace the 18-55mm kit lens next with the tamron 17-50mm f/2.8 or the sigma equivalent. I always see people on here saying to invest in glass over camera bodies but I am not so sure anymore. If I were to upgrade my D40 to the D90 or D5000 id be able to shoot at higher ISOs. I feel like id be getting better low light performance if I upgraded my camera body over my lenses at this point. Which brings me to my next question, is the D90 worth the extra money over a D5000? The biggest difference is the ability to use lenses without an autofocus motor built in but besides that are there any big differences between the two? Thanks!