What should the additional DME do to OG?
It will boost it by about .010, give it a bit more malty character and increase the Alcohol content by about 1.25% - probably just the thing you want if you're going for the Octoberfest type beer.
Unless you can ferment in about 50F and lager the beer properly, you should probably rethink the Wyeast 2633. The Danstar Windsor would make that into a fine beer. I'd avoid the Octoberfest style yeast unless you are certain you can ferment it cold and then lager it near freezing. We'll maybe you can do without the lagering, and just keep your bottles in the fridge for several weeks before you drink them, but fermenting that beer on the cool side with that 2633 yeast is going to be a must.
Regardless it will probably be a good beer around 6.25% ABV I think. That Willamette/Vanguard hop combination looks pretty promising. I've brewed a lot of beers that were real similar to that one this year ( http://www.homebrewtalk.com/f62/lawnmower-lager-kolsch-cream-ale-90175/
) because I scored a pretty big haul of Willamette that I've been trying to use up, and because I got some cans of Cooper's Light LME pretty cheaply on special.
I think it will turn out to be a good beer, I would certainly drink it.