Never bought camera gear through Amazon, but everthing else I've bought through them has been problem free. I would suggest Crutchfield. The cost is $3,499, but you get Crutchfield rewards which would be 5% of the toal ($174.95) to spend there later. The credit never expires and it is free to sign up for the rewards program. Additionally, if you know anything about Ebates, you can access Crutchfield through Ebates and get another 2.5% cash back ($87.48) for which they will mail you a check for that amount. I just bought a 5d Mk III kit from them and used this process with no problem. Crutchfield is also a highly reputable dealer.
I would second this.
I'm an amazon prime member too and buy about 99% of all my purchases through them....no tax to me where I live (yet)...
However, I bought my 5D3 with kit lens through crutchfield, plus the 85mm 1.8 lens...I signed up and got my sign up rewards points, plus at the time I found a code for the month of May, that crutchfield gave DOUBLE rewards points...so, in essence from that purchase, I have nearly $500 credit to spend on a new lens, which will likely be the 70-200 2.8L.
Also, I'd found that through amazon, that you might NOT get the current rebate on a lens with the special going on...amazon sold the 85mm lens I got from a 3rd party that was not honoring the double percentage off if you buy lens with camera...crutchfield did.
So by using the crutchfield rewards, plus a credit card (I paid that in full at EOM, so no financing charges)...I got $97 from credit care rewards and nearly $500 in crutchfield rewards.
I feel I got quit a bargain.
oh, and like amazon...on crutchfield, they have options for 12mo no interest financing....
Hope this helps,