Chris,
I find my EuroLX so amazing that it "scares"

me to think that the USA model is that much better. Oh my.
Maybe a stupid question but is it more the "feel" or the "sound" or both that makes you keep reaching for the NS-4 over the Doug Euro?
It scares me too. Your question about whether it's the feel or the sound is like on The Simpsons when Bart asks Homer if he wears boxers or briefs, Homer looks in his pants and says "Nope".
Really, It's both. Don't get me wrong, that Euro Doug is an amazing bass, I really love it, I would put it in the top 3 instruments I have ever owned. As simple as I can put it, for a while I had a Fbass 6 string that played effortlessly, but it just sounded to "polite" for my tastes. That Euro Doug sounds awesome, plays pretty good, just not as good as my Fbass played (all in my opinion of coarse.).
I keep telling my wife my NS-4 plays better than the Fbass, the best playing bass I have ever had, and sounds better than my Doug, the best sounding bass I have ever had and is one instrument, really I feel the bass I have been waiting to find for a long time.
So yeah, I guess both. I play it and can't believe how it plays, then I am just blown away by the sound coming out of it.
I have a little SWR combo amp at home, and at school I play through a Roland keyboard amp, still sounds awesome. Part of why I am selling Doug is to start the march towards the next American, but I would like to get a really good amp for home to hear what my NS-4 can do through a good amp.