Do I need a center channel?

[bighouse]

I have a KLH 5 channel 500 watt receiver and am currently running only two KLH floorstanding speakers that are rated at 250 watts a piece. I think these sound very good but I want to add a center channel to compliment them. I was also thinking about just getting a full surround package but I live in a small apartment and really don't have any room for surround speakers.

So my question is: would only having a 3.1 setup be worthwhile or should I just wait and save up for a full system. If the 3.1 setup would work, I was looking at the CS10 center channel. Would this compliment the speakers I currently have or would is it a bit overkill.

I'm new to the whole home theater thing and am trying to get started with a very small budget system so forgive me if I come off as very ignorant.