No that can be a good thing in some circumstances. Usually they go at a fraction of the cost and have nearly as much product life span left in them.
I have had zero problems with Refurb or even used products. (that weren't self inflicted

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I suggest you get the 705 and then save the rest of your 750 for other stuff. The 705 is receiver that can be turned into a pre-amp very easily if you find you need additional power. If your using 5.1 you can also bi-wire the fronts.
The THX modes are very good for movies and games. I highly recommend them. Although Direct is the best.