The most beautiful guns Ithaca produced is far and away their Flues. The wood Ithaca used, the checkering patterns and engraving are far and away the absolute best Ithaca produced followed closely by their Lewis Model. The NID is third, but for shooting the NID is tops!!!
Just my opinion, but get W. Snyder's excellant book about the Ithaca Gun Company and eyeball some of those pics, you'lll see what I mean.
I wouldn't hesitate to upgrade a Flues and get into reloading.

All the best