General Purpose Machines
Budget: <500USDThis is a fairly well balanced and affordable box which should be able to tackle most things thrown at it whether it be straight up work, gaming or something in between
Budget: <600USDA dualcore gaming oriented rig for $600 .. there's not a lot to balk at here.
Budget: <700USDThe extra $100 goes a long way to upgrading both the CPU and the videocard.
Budget: <800USDHere we've shifted the entire platform over to an X2 based system
Budget: <900USDAs a general purpose machine the 7800GT will prolly be the best allaround card to suit the task in the videocard department for some while
Budget: <1000USDThe extra $100 allows us to upgrade the harddrive and CPU here.
Budget: <1100USDUpgrading to 2GB as well as tacking on an aftermarket cooling this machine is more than able to tackle virtually anything thrown at it
Budget: <1200USDDoing a bit of shuffling, you can get an extra 200GB and improve the HSF.
Bigger Budget?
Anything after this price point and again I find my self looking to spend money so as far as reccomendations go, if you've got more money to play with (and the above specs havnt net your performance needs), make a post and we'll deal with it on a case by case basis.