Ditto the United Hobbies/Hobby City suggestion. You can't beat the prices. For 3D you want to get a 2:1 thrust to weight ratio. So if the plane is going to weigh 16oz including motor, battery, etc, then you want about 32oz of thrust. Naturally if you don't need crazy 3D power, any motor esc combination that'll give you a 1:1 or better thrust to weight ratio should work fine, but for me, I can never have enough power.....

The 3dbatix planes are nice. I built one of their biplanes and I was happy with the plane. I think that their Extra has been very popular.

www.RCGroups.com has a ton of free plans in their scratch built section. I've downloaded, built, and flown quite a few of them from their site.