Excuse me, but you don't know me well enough to make that judgement.
True I don't but I have answered enough questions to make a guess.
First of all, I have a degree in Electrical Engineering
Fine so do I.
that doesn't mean I'm stupid
I never said, nor implied you were. However some of your responses suggest that you have less experience than you are implying you have by your last post.
I've already bought most of the parts
That is what worries me. You need to make a realistic prototype of a tiny corner of what you plan, run it at the rate the real thing will run before you know if your design is feasible.
I've already made an 8x8x8 cube
Good so you know what is involved with 500 LEDs, now you want to scale it up to 3000. Scaling up is not easy, you don't just make more. There are lots of things to consider with switching so much current so quickly. I would have thought the TLC5940 was not the best choice as you have to synchronise the multiplexing to the refresh rate.
Best of luck with your project. Please post in the exhibition section when you have it working.