I have heard the stock model and it performs great for the price. Don could only make it better. Don's mods on the Marantz include adding a Hi-Blend, which is missing on a stock model, the same as the Mitsubishi.
Also read the HiFi Choice review. They gave it a Best Buy. They also openned it up and found the electronics inside to be as good as the $600 to $1000 tuners they were also reviewing in that issue. Just the case and cosmetics were of cheaper quality (should be for the price). The link is:
http://www.hifichoice.co.uk/review_read.asp?ID=1073