xd9x19
In my mind there is a significant difference between Nickle and Stainless with Stainless winning that competition hands down.... Nickle is just a finish applied to the barrel - stainless is stainless all the way through... Again in my mind I would prefer Stainless, then blued, then nickel...
of the three guns you listed - the optima is probably the most modern (newer features) than the Wolf or the Knight with the Knight possibly being the better. I am not much into the NEF - it can get really dirty in the breech area.
Another you might want to look at is the TC Black Diamond
and the Knight Big Horn
Hope I have not confused the issue.... but I have one more thought you can get an Omega Z5 which is a top quality rifle fairly inexpensively and it be a gun you can used when you really get hooked on ML's...
$286 @ Buds...
http://www.budsgunshop.com/catalog/product_info.php/cPath/36_440/products_id/17877
I thought I could find one for $250 - they are out there...
Might check this page out...
http://www.cheaperthandirt.com/complete_eeb.htm