First snow today! Not enough to stick... and good, 'cause my snow tires ain't here yet!
<a href="http://www.flickr.com/photos/uksi/4016793642/" title="First snow! by ilp, on Flickr"><img src="http://farm3.static.flickr.com/2633/4016793642_7ff1ee374d.jpg" width="500" height="375" alt="First snow!" /></a>
Steel wheels for $142 each?! That's a lot! Check out tirerack.com... I put in a 2008 MS3 and there are 16" wheel packages with $55 steel wheels and $96/100 alloy 16" wheels.
I definitely agree on going with 205 width tires.
I'm not sure if the 2010 MS3 fitment is any different though. You want to be careful about the offset. I think the craigslist link Zach posted is 38mm offset, so that may rub.
Update: did a little research....
2009 MS3 has a 18x7 stock wheel with a 52.5mm offset, and the 2010 MS3 goes .5 wider with the same offset (52.5mm). So I don't see why the fitment would be all that different for snow tires.
If I go to
TireRack and put in 2008 MS3, and click on View Preferred Package... that's $744 (plus about $75 shipping) mounted and balanced (VERY WELL I might add! so no vibration). The packaged wheel (Sport Edition F10) has 50mm offset, 7 wide, weighs 17.5lbs (not bad), and you get a 205 width tire (better snow traction). Hells yeah.
If I do an almost-bottom of the barrel setup (can't bring myself to recommend Firestone Winterforce to anyone) and go with 205/60R16 Dunlop Graspic DS-3 ($77 ea) and 16x6.5 steelies, you're looking at $528 mounted & balanced + shipping.
If you want to retain some kind of a "fun to drive" factor with snow tires and get better dry traction and responsiveness (but give up some ice traction and a little snow traction), then you can opt for "Performance Snow" tires. In the 205 width, I see TireRack offer Michelin Primacy Alpin PA3 for $144/ea... pricey, but those are pretty good and won't be quite as mushy-feeling as a regular snow tire.
Another edit:
OK, I noticed stock tire size is 225/40/18, which is a little smaller than the old Mazdaspeed3 size of 215/45/18. Against that, TireRack's recommended 16" tire size is a bit too large (2.4% larger). You'd be better off with 205/55/16 tires, which are 0.8% smaller (so closer to OEM). You can use
this Tire Size Calculator to compare tire sizes and their effect on the speedo. 2.4% is not that big a deal anyway... 205/55/16 snow tires *are* more expensive (so the same Blizzak WS60 tire is now $107 instead of $77).