If you are just using 2D animations, and not 3D I would just stick with what you have. The Quadro line is very expensive and is mainly for graphic/processor intense programs. If you absolutely wanted to upgrade, you could pick up a NVIDIA GeForce 550ti at newegg for $99 after rebate. That would give you much more processor power than your current.
Core Clock: 900MHz-975MHz
Processor/Shader Clock: 1800MHz-1820MHz
Memory: 1GB GDDR5, Memory Clock: 4.1GB per/sec
P.S: I would upgrade because you OpenGL version is only 2.1. The 550ti is version 4.1. It also supports DirectX 11. After Effects' minimum requirements are OpenGL 2.0 which you match, but for future versions they may need a more up-to-date version.
Hope that helped,