I second hillmanant sentiments. Building is really easy. The place that your most likely to run into problems is selecting incompatible parts. As long as you post on the boards this shouldn't be a problem.
Nevertheless, if this is for a business purpose (which it seems like it is) your probably better off buying a prebuilt system with good support. That way, if something goes wrong, you don't have to worry about it and can concentrate on work rather than being your own personal IT guy.
Looking at the website for this company, I'm not sure they have what you need for Maya, etc. You should really get an AMD FirePro 3D or Nvidia Quadro FX and all of these computers seem to run consumer graphics cards (Radeon HD and Geforce). It does, however, seem that they are using quality parts (including the powersupply and the motherboard) so if you're alright with consumer grade equipment then this company might not be a bad idea.