Do you live near microcenter? currently it's 50$ off 1155 boards when you buy i5 2500k @ $180. there were some Z68s mobos @ $100 before the discount. so for $230 you can get a better CPU with the same chipset. it's kinda useless to put and i3 2100 in a z68 cause the chip can't be overclocked and has no turboboost, if you don't need usb3 and sata3, you can get and h61 board for 20$ ontop $100 i3-2100 @microcenter.
people in this thread seem to believe the i3-2100 is faster than Phenom II X4 http://hardforum.com/showthread.php?t=1598673