I am looking at either buying another 8500 to put in sli or splurging and getting an 8800gt or an hd3850, will the latter really make that much more of a difference at 1280x768?
I would say if your staying at that resolution for a while go for a 3850 they are cheaper and perform very well bank for buck. Plus it can be o/c'ed to almost 3870 standard on stock cooling. Is this a 256 or a 512 8800GT your talking about?
Dual 8500s will give very low performance, putting two very low performance cards together will not give you good results. A single 8600GTS will hand it to dual 8500s, let alone an HD 3850 or 8800GT
I'd still nudge you towards a 3850 even if it's 256 or 512. At your res most new 256 gfx cards are plenty. Getting a low end SLI setup isn't the greatest idea anyway it's better to get x1 nVidia card or x2 ATI. Two 3850's whup ass bank for buck. Here's a link to help you make your mind : http://www.tomshardware.co.uk/forum/246966-15-3580-8800
I'd get the 8800GT over the HD 3850, unless the 3850 is easier to find or cheaper, which seems to be the case at the moment, so if you are buying soon, HD 3850 is a good choice. A 256Mb should be great for that resolution.
Either way, its terrible for gaming, I have no idea how you even tried to play games on it, get a dirt cheap HD 3850 256MB for $170 or stretch it and get the 8800GT 512MB. It's your wallet.
There was an article on this somewhere i read. 8500s in sli were only equal to something in between an 8600 gt and 8600gts. In short, get a better card than an 8500. I think this might be it:
Its in german but if you click on the 2 thumbnails on the left it shows 8500 sli performance in prey and call of duty 2. In short, its terrible im afraid.
also remember, SLI doesn't give you a consistant performance increase across the board, which means it'll perform better in some games, and some games won't even see a change.
IMO, buying one good card is better than 2 crappy ones......