I use newegg or ncix, ncix is local to me, as well as Canada computers, but I'm assuming you are not in Canada. I'm not sure what part's distributors are local to you but I'm sure a google search would inform you if you don't already know.
The 3770 should suit you well, I can only speak from experience and I don't have experience with everything, but it is still high end!!
I wish you luck with your build and hope everything works well for you, if you ever need any type of assistance feel free to PM me.