I tried searching for some info...but I got seriously confused.

What is the speaker sizes for the RX-8 without the Bose system? Some people said 5 1/4" will fit and so will 5x7s and all that. I think the rear are 6x9 and the tweeters are 2"

Can anyone please give me some clarification? Thanks alot!

6x8 front, 6x9 rear. 2" for tweeters sounds about right.
6 1/2 will fit fine in front with the use of an adapter plate.
5x7 speakers often will have mounting holes for a 6x8 location.