It's hard to make recommendations without data. "Summer wheels" implies that you think the OEM wheels to be for other seasons. So: which? Winter? Fall-Winter-Spring? What? Where are you?
My tastes run to beefy wheels (sort of like those in the picture) on Outbacks, but there are many 18" options for summer tires that will improve handling. We have 18" Subaru OEMs from our Legacy GTB on our Outback, for example (I've posted too many pictures of this already to justify another).
If your Outback is white, my personal choice would be silver-ish wheels like those in the picture (not white; certainly not black). HPH
Onto my white Acura TL, I just installed a set of Sport Edition KM11 wheels in a dark silver (I guess it would be called gunmetal - the web page calls it silver, but the picture color is accurate.) The color is a little translucent and looks a lot like black chrome. They are very sexy and easy to clean. Mine are winter wheels, but "easy to clean" is good, year round. The back side of the wheel is painted gloss black. The downside to this color is that it will be really hard to touch up curb rash.
You really need to tell us what size and how much you want to spend. The Sport Editions are low end, but decent quality and a very good buy. I prefer thin spokes and not very many, since this allows you to clean the back sides and calipers. I hate dirty rims and calipers....
I'm in the same boat, trying to decide on what wheel to get for a white 2012 (figure I wait until the original tires wear out). I keep coming back to to black wheels. I'm currently leaning towards Enkei EKM3s.