Okay, so here's the situation. I have a 8600GT 512MB DDR2 graphics card. System is running a Q6700 2.66 ghz processor, 4 gb 800mhz RAM, Vista x64. I do not do any gaming. My primary use of the computer is typical business usage (web, email, etc) and photo editing and some home video editing. I recognize the graphics card is a weak link in my system (as well as my PSU ~ 360 watts). I'm trying to figure out if I really gain anything, given my usage, by upgrading the graphics card which would probably also likely require a new PSU?

Another thought would be that if it doesn't really give me any tangible benefits to upgrade given my usuage, does it make sense to still upgrade it now - even though I don't need it now but might in the future as things change - while the parts are readily available and prices are good?

To get a decently performing graphics card, yes, you will need a new psu. Q6700, being 65nm quad, is already taking a large chunk of the 360w psu's power output. 8600gt is very weak, but if you don't play games, it'll do fine. It's good as is.

man
you answered your question man
your computer is more than enough if you dun play any games
unless if you use it for VERY EXTENSIVE video editing then dun upgrade
there is no need

and on the point that prices are good
yes i know prices if video cards are good right now
but there has never been a video card in history which prices has gone up during its life span
prices only drop as time go by for computer parts or electronics in general

so i dun see any rush for you to upgrade at the moment man