speaker locations

There are kickpanels out there for just such a project. The ones I got use 4x6 speakers. I think there is another version out there that take round ones, but not sure what size. Here is what mine look like now that I painted them and the grilles.

I've seen those on ebay for $124, is there anywhere you could get them cheaper? And they say Dart Sport, but I'm assuming they'll work with a normal Dart too..