Could someone tell me where's the best place to order a Onkyo 706 online
Do not buy from CC! You're hosed if the receiver doesn't work, you don't like it, doesn't have the right features, produces blue dots, etc.
I just got mine from Amazon. It's $549 and qualifies for free shipping (Free 2-day shipping if you are a Prime member). Only catch is you pay return postage if returning for any other reason that "it doesn't work". At 41 lbs. that could be quite a hefty bill.
Crutchfield has it for $599 and will pay return postage if you choose to return it for any reason.
J&R and 6th ave are frequently mentioned here. I don't know of any brick and mortar chains that carry it.