I'm curious if you've priced out a 12 VDC, 300+ amp power supply; your budget already sounds like it going to be fairly large (it would have to be, for the number of linear actuators you want won't be cheap), but have you planned out how the power will be distributed or supplied?
I don't think you're going to drive the whole thing off of one power supply; multiple smaller supplies will likely be needed - but once again, it won't come cheap...