If you're not going to CF/SLI, aren't going to be pushing high OCs, and don't need a lot of expansion room - if you're looking for a good motherboard that is cheap - try the GA-P55M-UD2 for $105: http://www.newegg.com/Product/Product.aspx?Item=N82E16813128405
If you want to do some reading on the micro's, here's a review from last October of the Gigabyte GA-P55M-UD2 and an ASRock mATX: http://www.anandtech.com/mb/showdoc.aspx?i=3652
And Tom's recently did one on those two mATX's plus an MSI and a Foxconn: http://www.tomshardware.com/reviews/microatx-p55-motherboard,2524.html
By the way - with an i5 you will not be able to run your RAM at 1600 MHz without OCing your CPU/chaning your BCLK. There are still good reasons to get 1600 RAM. For one, it may be cheaper than equivalent 1333 RAM. Also, while keeping it running at 1333 you might be able to tighten the timings or lower the voltage. Just wanted to make sure you knew it wouldn't run at 1600 unless you OC'd.