OK.... I will ignore the little man behind the curtain.... er, I mean the interesting home theater room...
Don't be putt off my anyone suggesting to you that inexpensive drivers won't work. My own system uses a 3.5 inch driver that was widely sold on the internet for $3.00. No one knows why Sammi of Korea thought that they could sell their 3 mm xmax little speakers for $17, but the couldn't and eventually they just unloaded them. I also used a very fine but inexpensive Dayton neo20FA tweeter because I love domes that are not driven hardly at all, and that can have their flanges cut to a C-to-C of about .80 fixing the comb filter distortion at beyond most people's audibility of 16,500hz+.
Suppose you build this? What were you considering for your tweeters? And what is the individual sensitivity of 4 x 6's? You do need to consider the c-to-c between the tweeters and Mids and the elongation might set that up as a problem horizontally.