This is definitely a YMMV, so don't shoot the messenger...
Target has the UN55MU6490
for sale for $599, which is same as just about everyone else.
However - at least at my local target they had the UN55MU6500
for the same price (retails for $699 right now, past sales have been ~$649)
It had the same store ID (008-09-1102) as the 6490 (see attached images), so this may or may not be a common "mistake", hence the YMMV.
The link is for the 6490 so you'd reccomend to purchase it in-store to make sure you're actually getting the 6500.
As a bonus and an even bigger YMMV, the TV was on display with "SALE $499" around it which they did honor after some haggling (it rang up $599 at first).