Crutchfield is a good place to find out sizes and whatnot. You may can find speakers cheaper elsewhere however c/f supplies wiring harnesses for "free". MB Quart is a brand that I personally like. Happy Hunting.
YEa if not , go ahead and go to bestbuy , circuit city , brandsmart. Crutch field is good tho , my brother orders his speakers from there and they came out good. I like Pionner stuff: Tvs , speakers , woofers. Nice
The only half decent chain store around is Tweeter. At least in my area. Circuit City and Best Buy sell stuff that's made for them. e.g they have Alpine, but nothing you'll see on the Alpine.com site.
MB Quart 6.5" fit up front with no real mods. You'll have to put some spacers in front of the speaker to keep it from hitting the door panel at full excursion, but besides that, they'll fit. The front doors are very shallow. The space will fit nearly any 6-1/2, but the problem is the door panel.