When shopping for sway bars, and consulting my shop their advice was to go as big as you can in the rear (but also making sure its adjustable) and the brands the recommended were Cobb, Hotchkis, and Whiteline. Pretty much in that order, and the endlinks the recommended were either the rallitek or the kartboy endlinks. I rode in 2 different STIs before, one with whiteline (kartboy endlinks), one with Cobb bars (rallitek endlinks). I honestly couldnt feel the difference in just riding, but I knew that both cars rode and handlen much better than my stock setup.
"2007 WRX- PPG'd, 20G- Tim Bailey tuned
Stage 2 2005 WRX