The MTX's you have there will not need an enclosure as they are "infinite baffle" speakers. The Polk is not and will require some sort of enclosure. Sealed or ported or what size I don't know.
I would go with the MTX. They are only 200 watts so don't blow em up
When I was a child, I used to talk as a child, think as a child, reason as a child; when I became a man, I put aside childish things.
1 Corinthians Chapter 13 - 11