Go Here:
http://www.tomshardware.com/
Its a great site, and the best part is they concentrate on what
you need and not just what the latest and greatest is.
1) Unless you do a lot of design work or video production, there is no need for a quad core. Most software outside of video and design still isn't advanced enough to exploit multiple cores.
2) Unless you game a insanely high resolutions, or have a huge monitor, a single video card solution is best for you. 17-19 inch monitors look great with a Vid card below $100. if you want all the AA, then you'll have to move into the $100 - $200 range. Also, when choosing, remember that games are designed to run on specific GPU's/GPU drivers, so check your favorite games to see what they "run best on". It really does make a difference.