What 6x9 Speakers

I never run rear speakers just fronts and a sub, not a fan of the music coming from behind me.

I wouldn't run 3 way speakers either, component or at most 2 way.

I imagine there's not much difference between the two, I probably go with Polk mainly to be brand consistent (with fronts) and better power rating. Best is to find a shop where you can compare them.
I would say it probably doesn't matter much....read some reviews perhaps. It also depends on what you are looking for. I went down the hi fi stereo slippery slope a couple years ago and I would agree with the above. If I built a top notch stereo I would spend all the money on high quality 6.5 speakers and a sufficiently powered amp to drive them. I doubt putting something behind a kick panel will yield fantastic results though.