Just pulled the trigger on one of these babies....
Well, yes, there is only .05 output difference which does seem tiny - but placed within context. That equates to 25% less output than your current, very low output, cartridge.
Yes, Denon are a large company but so are Audio-Technica and they have certainly made some cartridges that are not to my taste. To be honest, it rather sounds like you have decided that you are going to live this cartridge whatever.
I read Jerry's review of it and his comments regarding poor bass concern me (though he doesn't state what phonostage is used) - I've owned Denon cartridges in the past and reticent bass is not a characteristic I remember.
Regarding high frequency output, that is definitely a factor of low tip mass, low moving mass (low output suggests few coil turns which is good) and stylus profile. The Denon says it uses a modified elliptical - it would be interesting to know what this means exactly but on the face if it there are significantly better profiles available (including the one fitted to your own SPU).
If it does go above 20k though you will need to consider some super tweeters for your speakers. I was very pleased indeed by the results when I built mine.
http://www.homebuilthifi.com/images/...k_together.jpg