my 2004 chevy avalanche speakers blew out. What size speakers should i get to replace them for the best price?

Yeah use Crutchfield they not only take into account the diameter but also depth

Also Crutchfield will include anything you need to install the speakers. I bought new ones for the front doors and they sent adapters and the plastic mounts. I even bought the speakers from their outlet site they were open box

As the others have said, Crutchfield has a great selection. According to their site, the 2004 Avalanche w/o Bose can accomodate 5.25" and/or 6.5" speakers in the door. If you have tweeters in your A-Frame molding, then you may want to look into the Component options that Crutchfield has; that will provide you with the Mid-Bass / Mid-Range Driver for the door & separate Tweeter for the A- Frames. Coaxials in the rear door are a good option. Coaxials (Mid-Bass & Tweeter drivers in the same chassis) are a good option and normally cost less than Components (Separate drivers), but can still offer very good quality sound. Don't expect back massage bass from a 6.5" mid-bass driver, but I've been impressed with the solid mid-bass response on the 6.5" drivers on my 2009 Avalanche; still trying to figure out if I can get a sub in there and not sacrifice usable area (family / daily driver vehicle).