Ideally you want the tweeters of your LCR speakers to line up, or as close as possible. Tilting the centre channel upwards slightly can help as usually people have it set up under the screen/TV. Axiom speakers are tapered cabinets so placing your plasma on top of the centre channel would be a no-go. Even if they were parallel I wouldn't do it anyway(if it were me).
If you don't mind me asking, why wouldn't you place it under the TV? Do you think it would impact the acoustics of the speaker or would be concerned with the cabinet being able to handle the weight? Or just that the TV might fall off?
I think I will eventually wall mount my TV, but not something I could do right away, so just curious if putting the TV on top of the speaker would be good enough as a short term solution.
