Hi Guys, I am in need of your expert opinions: I have been shooting with the Canon Rebel Xsi for nearly a year using the Kit 18-55, the 55-250 tele, and the 50 1.8 prime. I have been enjoying the camera but I think it is time for me to upgrade the glass. I was looking at both the 70-200 f/4 and the 17-55 f/2.8 IS. I was leaning towards "L" glass because I think I might want to upgrade to a full frame camera later on (when the mkii goes down in price). I think most of my shooting is done within 100mm so maybe I should look at something like the 24-105L which leaves me with the possibility to always upgrade to a FF camera. I then realized that maybe I should switch over to Nikon before its too late, I do alot of night shooting and I hardly make any big prints so more MP does not make any difference for me. I was looking at the Nikon D300 or D90 but then I would also have to buy new lenses something I am willing to do. If I do go this route I have someone who is willing to buy the Rebel with the lenses for a fair price, so that would not be a problem. Is the difference in noise between the Nikons and Canon (mkii) so obvious or will I not see the difference, I cannot shoot above ISO 800 with the Rebel before the image becomes unusable. What do you guys recommend? Upgrade? or Switch? Thanks guys.