[quote name='EBS_freak' timestamp='1426552830' post='2719346']
Try them however you like and stick with the arrangement you like.
[/quote]
Is the only correct answer.
Speaker size is only one factor in many that influence the how a cab sounds.
[quote name='lowhand_mike' timestamp='1427724279' post='2733464']
in some cases it is to get a lower impedence and get the full power from the amp, i know mine works that way
[/quote]
Nah, you don't get a bigger sound from using more power, you get a bigger sound from using more cab. Try using 8 ohm cabs and 4 ohm variants of the same cab, the 4 ohm cab, although using more power, won't sound louder. Just more likely to overheat your amp!
Furthermore, having an amp than is rated for lower impedance is okay, if you're into that carrying needless weight around thing . Myself, I prefer a powerful amp rated for higher impedance and cabs to match. The transformers are lighter, they generate less heat and so are smaller and lighter as a whole.