you missed a great deal on an 8800GTS by one day, yesterday this Zotac 8800GTS was $119.99 after rebate, today the price went up $30 to $149 after rebate, still a pretty good deal for something that beats an 8800GT or a 9600GT...
throw that in there and you have your Intel/Nvidia build, but the 4850 beats the pants off the 8800GT, 8800GTS and the 9600GT, so you'd be dropping in performance to go that route, you'd be adding $70 to the build above, but would get $40 of that back, plus the other rebates in the build, so it would probably end up being around $500-$550...