Speaker question

I'm putting together a stereo system for my e31 and I have decided what speakers i'm going to go with. I'm just on the fence about which size would be easier to install in the stock locations, 5.25 inch 2 way components or 6.5 inch 2 way components. I was just wondering if I could get some help deciding. I know modifications will have to be made to make any speaker fit in the 8 series but I would like to make things easier if I can. I'll be installing my mid speakers in the kick panels and tweeters in the doors behind the speaker grill. As for the rears I will be installing 2 way components on the rear deck. Here is a list of the hardware i will be using.

Hardware i already have.
alpine cda 117
alpine pxa h701
alpine rux c701
alpine pdx f4
alpine pdx m6

Front and rear speakers and subwoofer im planning on getting.
Audison Voce AV K6 (6.5 inch) or Audison Voce AV K5 (5.25 inch)
Audison VOCE AV 12

Speaker question