You will want a third, much larger, hard drive to keep your footage and renders on. One SSD for the OS and programs and one for the cache is fine, but I'd want a bigger drive to put everything else on.
The Quadro is certainly overkill for After Effects work. Barring third-party plugins (like Element 3d), AE only uses the power of the GPU for certain few things. Read about it here. Even if you use Element 3d, the card is still overkill.
The power of Xeon processors is really shown in that you can have more than one in your system. This is great for 3d software, but not so much for AE. In the current version of AE, AE is not very good at utilizing multiple cores, much less multiple processors. For some projects it works really well to render on multiple cores. However, for some projects, it actually makes it worse. Unless you're planning to put two Xeons in your box, I would consider getting the lower class of processor. And, whatever processor you get, I would get one with fewer cores and a higher clock speed.
Now, keep in mind that all of this processor talk is related to the current version of After Effects. I am very hopeful that they will sort out the multicore and multiprocessor rendering issues in a future version and get AE up to the blazing speed I think it could have.