alright so i'm looking to make that big jump from pc to mac. been using an HP laptop the last few years and i've decided that of the machines apple has to offer me, the iMac would suit my needs best. my only problem is that i can't decide between the 17" and the 20". i'll be using it as my main computer and possibly doing some gaming... harddrive space isn't really an issue. is it worth it to upgrade the processor on the 17"? what about upping the ram to 2 gigs? if i were to decide possibly upgrading at a later date after my purchase, would i be able to install ram myself or have to take it back to apple? how much of a difference is there really between the screen on each model? another question about the monitor, i'm at college right now and i get to work on an imac 2-3 times a week. is there any way to tell for sure what size the monitor is just by being in front of the machine? other than bringing a ruler, obviously. i may come up with more questions but thanks in advance to anyone who answers.