if u want the performance and handling to remain, search for the rims and tires with the same specifications going smaller or bigger will affect fuel consumption, power to the wheels, reaction time, handling, and so on even if it is a small change...

many m2 users change to the same size meeting all the same spec and everything is going well
some lower their car, still works well, most probably thanks to good services
all in all....be careful and be sure to get ready to face the risk
http://forum.lowyat.net/topic/1557876/+1580
nevertheless, changing the looks of ur car shoes would rock ur world all the way haha..i've seen many that changed theirs and the car looks awesome!

a lot go with enkei and certain bbs..
as for tires, for me, i love bridgestone/dunlop.. never fail me until now in my car.. i'm not using a mazda2, however ive driven many

last but not least...i would suggest u to ask in mazda2 thread