Small 2-way delivering 90-20k - in need of serious guidance

I started a thread similar to this in "Fullrange" but realize now I should have put it in this group.

Design goals:
  • 57" wide LR soundbar
    • LCR if space permits, though I do not have surround at the moment
  • Completed assembly weigh less than 50lbs
    • I need to mount the soundbar to the full motion tv mount, cannot wall mount or place on cabinet.
  • 90-20k response
    • I'm limiting low end response in an attempt to keep the design compact and weight down.
  • This will be used with a subwoofer to cover 30hz and above
Reason:
I'm going to remodel our family room.

Why the design constraints:
  • The television is mounted to a full motion arm in the corner of the room.
  • There will not be a suitable location for bookshelf or floor standing speakers, and no console below the television to place a larger soundbar, etc..
  • Since the television is pulled out from the corner and floating in the room I would like to mount the speaker solution to the arm holding the television.
    • The arm can support more than 120lbs, the television weighs about 60lbs.
  • We do not have surround sound but I think it would be smart to include a center channel for future use, if that is a viable option.
  • I am not attempting to create a THX standard levels in my family room; I simply would like better sound that the speaker on the television.
    • I currently use Elac UB5 speakers when watching movies. There will not be a suitable place to use those after remodel.
About me:
I am an accomplished woodworker and have built a pair of subs,
I have never design/calculated/built a multi-way speaker. Basically, I do not fear the construction and I do recognize my ignorance when it comes to speaker design.
My actual stereo for music listening is in another room of the house; this is just television.

If I can keep my parts cost (drivers and crossover) below $400, that would be fantastic. Lower would be even better.
I'd like to believe my goals are reasonable and I am being completely candid and honest about my knowledge and abilities.
With all that said, please be kind.

Thank you in advance