For my current project, I can specify the system that will display Unity. I need to have two screen display of a flight simulation with big terrains, textures, a lots of models. I'm thinking of something like a workstation system with a Intel Core i3-540 Processor (3.06GHz 1333MHz 4MB), Windows 7, 4 GB RAM, NVIDIA Quadro FX 580 32-core (512MB DVI+DP), 2 x 1280 x 720 display (one's a video projector).
Would more system ram, video ram, or processor speed help performance and/or maximum amount of objects and textures? What would give me the most bang for the buck?
Are any types of video cards (Nvidia, ATI, etc.) better for Unity?
UnityAnswers is a place for questions that can be answered! Avoid asking questions here that are subjective, argumentative, or require extended discussion.
Though I'll do you the courtesy of answering your question for you, this topic would be better suited for the forums.
Working on a high-end system is always nice, but this isn't really a good question, and I'll explain why.
Computer hardware is always evolving. The minute you buy a high-end system, something else is going to beat it. And when you develop on such a high-end system with Unity, you forget about those people who are going to run your game that have less powerful systems than you, and won't be able to run your game.
Unity is very optimized. Your system should be able to run it just fine, and if it can't, then you need to work on optimizing your game more. If your game is running slow, it's not because you need a faster computer, it's because you need to optimize your game more (reduce texture sizes, tweak Mipmap settings, optimize scripts, etc).
Basically, there is no "good hardware" for Unity. So long as your computer isn't 8 years old, you should be able to run it at fairly decent speeds. And if you find something that IS sluggish, you need to use your own problem-solving skills to figure out what the bottleneck is in your system, and then upgrade that component.
Unity Authoring (Editor) System Requirements
Windows XP SP2 or later; Mac OS X "Tiger" 10.4 or later.
Graphics card with 64 MB of VRAM and pixel shaders or 4 texture units. Any card made in this millennium should work.
The rest only depends on the complexity of your projects!
Unity Player (Runtime) System Requirements
Windows 2000 or later; Mac OS X "Panther" 10.3.9 or later
Pretty much any 3D graphics card, depending on complexity.