Woah. Now that's not really the case. Center Channels are just a different type of speaker. Speakers are designed to reproduce sound.
I use a normal speaker for my center channel actually. Works great too.
The separation part depends on your room size and many other factors. But think about it this way. Would you rather have 2 300 dollar speakers or 3 200 dollar speakers. It's a question you must discover for yourself.
Try life without the center just to experiment. If you find you like it then you just saved yourself some change. If you find you can't live without it then you just discovered you need one.

Either way a bad center isn't better than no center.