Check out the CMP also. They are getting in 223 ammo periodically. I thought that the following was pretty good. From what I saw on the online ammo sites this was less then them. Its the slightly heavier match round (62gr) from Remington.
4C223R62 1 Remington .223 Rem. Ammunition $130.00
200 rd/cs
They currently have various Black Hills, Federal and Winchester 223 ammo in stock (besides 22lr, 30-06 and 30m1).
As for Dicks don't forget to get their SCORECARD. When you spend 300 bucks you get back 10 bucks for next purchase. So if buying a lot of ammo you might want to break up a purchase into several buys. And if you buy a the case, you get a discount.
Finally, Remington has some rebates on ammo going on. You can check out their coupons at:
http://www.remington.com/library/promotions/2008_load_up_on_savings.aspEvery little bit helps !