User Manual Klipsch R-52C Audio Speaker

I believe it is still an upgrade, but not sure by how much. I purchased mine to replace an onkyo center from a kit. We used to sell polk and klipsch when I worked at hhgregg and klipsch was a higher quality.

Probably not overbearing but the size of this thing is the same if not slightly larger than those (I have the r-51ms so basically the same thing). In terms of timbre matching it's really you're only decent choice since other klipsch centers are massive.

Not without a bracket. It does not have the slot in the back that the bookshelf speakers have to be mounted on a single screw.

No. It will not hold still in upright position. The speaker is only designed to lay flat as far as I can tell.

It's not much bigger than the product itself. Comea with enough packing material that it may make the box 4in larger in each direction than the product.

Yes, the center channel speaker is used to provide better voice dialogue in a surround sound system. Not sure what you mean when u say "use this speaker on its own".
Can you use this center speaker on it's own for better voice dialogue when watching movies ?

Not directly from the speaker cabinet, but you could use a shelf or a shelf-like center channel wall mount bracket to put this to the wall. On Amazon you could search WALI Center Channel Speaker Wall Mount Dual Bracket Holder Stands for an example mount. The R-52C dimension and weight are Height 7.3 inches / Width 18.75 inches / Depth 7.6 inches / Weight 13.5 lbs.