Here's an example of what happens when you put on a TEIN Wagon S-Tech spring in the front and stock WRX Wagon spring in the rear. This is makofoto's car when he was having rubbing problems with his 225/45-17 S03's. he tried putting on the stock rear springs to get some height back. As you can see, not only is it higher in the rear, the much lower front actually pulls the rear spring up a bit making it even higher than stock.
Get a matched set like the Prodrives or Eibachs and you should be fine till your struts wear.