techronics.com, sonicelectronix.com, woofersetc.com are good sites to buy from. Don't buy from onlinecarstereo.com or dealercostcaraudio.com. Both of them will f*ck with you. I've read a ton of bad reviews about dealercostcaraudio to not even attempt to do business with them and I recently got screwed by onlinecarstereo. I heard from a few others after the fact that onlinecarstereo isn't the best to order from anyways. I got my issue straightened out but it took them a couple of weeks to do so. They shouldn't have f*cked up in the first place. Hope that helps you out in your audio endeavor.
Just ordered a deck and speakers from Sonic for a install. Got free dash kit and harness with the deck. Not all places give you them for free. And alot of their stuff has free or really cheap shipping. Ordered from alot of online stereo stores, Sonic has been the only one I use consistently.