i like crutchfield because they give you just about everything you need to install a head unit and speakers... wire harness for both head unit and speakers, replace trim piece, install docs with pics and they have great phone support.
if i'm familiar with the vehicle already and have the wire harness and/or trim piece i will also check amazon - put i typically only buy if it's actually sold by amazon and not another retailer.
I heard of crutchfield but thought they were expensive (idk maybe i'm wrong). I gotta check amazon!.
I normally buy electronics from newegg and tigerdirect.com. would you recommend them for car audio?
btw CAr came with old aftermarket radio so i wont need a kit and intall s/b easier than from manuf.