My opinion: +1 on Pale ale. Your summits are too much for pale ale and not enough for IPA. If it were me, I'd use about 3/4 ounce of the summit to get around 35 IBU and then split the remaining between 10 min and 0 min additions, and forget the dry hop unless you can get more Centennials while it's fermenting. But I like Simcoe, and I understand Summit tastes like Simcoe. I personally think Simcoe and Centennial are a nice combo, so I would try Summit/Centennial. If dry hopping, I'd keep it light. Also, if you decide to go with a pale ale I'd reduce the extract by a pound to keep it more balanced.
Just my .02, it's all up to the brewer. I just find that the more stages of hop additions you have the fuller the hop flavor will be. I find if I just do 60 minute bittering + dry hop, it really leaves me wanting something in the middle. Dry hop is nice, but I think the late additions are more important and only dry hop if you have the late additions as a "foundation".