If you want a link to sparky's free collision dll, there you go :
http://forum.thegamecreators.com/?m=forum_view&t=74762&b=5
Otherwise, Nuclear Glory is available trough google searching (you will be brought to their website, where you can buy it).
Newton can be downloaded here :
http://walaber.com/ndb/NDB_v132.rar
or get screenshots / demos, and a b-version ( ? ) here :
http://walaber.com/ndb/
I personnaly use Sparky's, which is faster than light (fwooosh!), highly effective and fullfill all my needs. Never tried the Newton one, so I can't help you here. I've tried a trial version of Nuclear Glory which was really impressive, full of features (80% of them aren't useful for my projects, but this is subjective =).
[Edit : forgot links, silly me :$]