Indeed: don't play with speaker orientation. A good designer/builder will make certain that all the issues of baffles and diffraction are dealt with to the best of their abilities! Turning a vertical speaker sideways can create suck-outs where you will lose significant SPL due to cancellations from that diffraction. Good center channels designed for horizontal use should be OK, but if you have the space, a like tower or standmount, matched to voice cortectly with your L/R channels is ideal.
This review by
@shadyJ shows the difference in using an MTM speaker horizontal vs vertical... very informative to see the effects of orientation!
Going back to that point... definitely consider looking into a matching center speaker for your rig.
@rgbbhat72, I don't want you to spend more money, but if you are more into HT than Audio, consider that that center channel is the anchor for a surround rig, and that the front soundstage is engineered for a cohesive sound. If you have two different Sound Qualities as sound is traveling left-right, you will inevitably be losing some of the impact properly matched speakers can deliver.