(Cracks knuckles) Definitely keep the P4 system; that would allow you to run a render on the fast box, and still do other things. The Athlon 64 would increase your rendering speed; if you only have a 32 bit OS, then it runs in 32 bit native mode. Something none of the Intel '64 bit' chips can do at the moment. You definitely would want the socket 939 version, as that one will be upgradeable to the dual core X2 with a BIOS flash; but keep in mind that it may take some time for the cost to come down into the realm of affordable. The first dualies out will be aimed at the enterprise market, and both companies are talking a release price around $1,000 per chip for the server version. No word yet on the desktop version's cost. But the Athlon 64 is simply a better chip in design and implementation; they routinely wax Intel chips clocking almost again as fast (with the exception of applications that have been specifically coded to perform better on Intel). Plan on a PCI-E board; AGP is being phased out as fast as they can get away with it. Plan on most of your storage being on SATA drives, as the PCI-E boards are configured to support more SATA than IDE (leaving the IDE ports for things like DVD burners, etc). YOu don't need SLI unless you are a power gamer, and whatever you do, stay away from the video boards with gobs of memory (unless you want bragging rights or are a power gamer). More and more video cards are requiring a dedicated connector to the power supply's 12v rail, or a separate external power source. And the heat the generate is impressive. The next Nvidia chip due out ths fall is specced out at 95 watts of power consumption (which happens to be about what 2 80486 computer =systems= would pull under stress). So keep adequate ventilation in the back of your mind, as well.