I upgraded a Marantz sr4002 last summer to the entry level MRX 300 and it was meh when I first connected everything. I loved my old Marantz and was feeling a little buyer's remorse, however once I ran ARC I quickly changed my mind - ARC is so cool, much better than the surround processing of the Marantz or the Pioneer before it.
Why you ask :)well because both the Marantz and Pioneer and many other surround processing programs focus on a "sweet spot" with ARC there is no "one" sweet spot. To calibrate ARC you must position your mic a minimum of 5 different spots (you can add more if you want) then your computer uses the ARC program to calculate the best sound for all 5 locations - in essence there is no longer a "sweet spot" since no matter where you sit in your area you will receive optimum audio.
Hope that makes sense - bottom line ARC is awesome
