Last thing I bought from them was my HDTV back in 2007. One Call typically only gives a 10-20% discount depending on the list price.
Depending on the Denon AVR, you might be better off just trying to work out a deal with a local shop. You can also go with Accessories4less if you don't care about it being refurbished but make sure you add a 3rd party extended warranty to your purchase. Checking EE and AVScience is a good suggestion as well. Might as well shop around.