If you don't want it to sound "real cheap" you might want a smaller midbass driver. It could be tough to find any tweeter that can play low enough for the 5.5" center-to-center spacing on the ones you linked, let alone a cheap tweet. Have you read Dr. Griffin's paper on line arrays? It would be better to go shopping with a solid design in mind. Your goals seem realistic, I just think you will be happier with the results after reading.