new upgrade opinions please

i have an AMD 3000 Radeon 9600 and 1 gig of ram. am thinking of getting a new motherboard with a duel core AMD 5000, 256MB GeForce 8600 GT and 1 gig of ram. on my current system i run FS9 at 1024x768. i can run it at 1200x1600 but get occasional stutters so i usually come back to 1024x768. if i get the mentioned upgrade do you think i can run FS9 at 1200x1600 without any stutters and i'm talking about with real weather but using 2D clouds instead of 3D. i don't mind the difference that much and it helps things to run smoothly. i also have everything else pretty much maxed out, most sliders far right. i also currently just fly the default aircraft so i'm not concerned about any addons BUT maybe that might be possible? mmmmmmm? how much of a difference would i see between the two systems? thanks, william