It is considered important to have the speakers all have the same 'voice'. When a home theater system is set up properly, the action and voices should move seamlessly between each of the three front speakers: for that reason, it is also important to be sure that the speakers are all the same volume. Most home theater receivers have some sort of pink-noise test-tone generator to help the user set the individual speaker levels properly: read the instructions carefully to learn how to accomplish that.

Get whatever center you want, you can adjust your volume in the menu of your amp.That's the biggest load of bull i ever heard, what if you went with the same manufacturer but went with a more high end speaker for the center (which most people do for the vocals in 5.1 surround) it would be no where near the same quality of the other speakers (despite who makes it)so get any one you want!!!!

Hmm conflicting opinions. Now what?

It all depends on how critical the sound is to YOU.

If it is important, follow Tigerbangs' recommendation. It it isn't, listen to Netlos.

Me, I agree with Tigerbangs.

Voice-matching speakers is a well-known concept when assembling a home-theater system from components from different manufacturers. Please read the link for a further explanation of the process.

Here is a link that might be useful: article on voice-matching speakers

Keeping the front and centre speakers the same is a well regarded rule of thumb in the sound world.
I was trying to make do with a centre speaker in my set-up (different make)because I already had one from a previous set-up, and I am changing it out.
The old one sounds boxy against the fronts that I have (and the fronts are keepers!), so out goes the old centre.