I have the 4100ose and an early upscaling DVI DVD player (non HDCP

). I still use the Marantz for most of my watching - probably due to the fact the remote from my amp controls it too - and can say that except for really well mastered material it gives nothing away to the digital path. I run both sources into an Iscan HD scaler.
If it was my money I'd wait until there was a creditable Hi Def product on the market before making another purchase and keep the 4100 for music and replace it with a CD player when it finally gives out.