Channel Speaker Center

can I use a floor standing speaker as a center channel?

I have a polk monitor 50 which will be alone once I buy two more floor standing speakers which are better can I use the single monitor for my center?

The cener channel of a surround setup must carry most of the dialog. As such a good "center" should have excellent mid and high frequency response and it's a mistake to skimp on the "center". That said, You can use any full range speaker, BUT since a center speaker should be on top or just below and centered on the screen I suspect a 35" high speaker won't fit vertically (thats why most "centers" are horizontal. You could turn the Polk 50 sideways, I guess, but you are not going to get great sound from the Polks in that configuration due to the port off to one side. So ... you could use it, but a dedicated center would be advisable.

Stereo Design Wilson Audio Mezzo CES in HD 2011