Note: this applies to extreme 3d animators for commercial and home use.
$500 is no way near the amount for a 3d animation rig. I am building one myself and you will need at least $1250 assuming you have a monitor and okay chass
You need a workstation graphics card, Multiple SSD in raid, Multi core CPU, 750+ psu, 32gb of quality RAM and a motherboard to support it all. If you're on a budget don't go for an Intel based rig....go for AMD...plus AMD is now working to expand openCL and gpu acceleration technology to products like Photoshop, adobe premiere pro, Maya, mudbox, 3ds max, autoCAD and more to come for sure. Use ASUS or Gigibit motherboard