Well, the advice you have so far pretty much covers the available options. Remember that the N frame was originally for the biggest traditional calibers -- .44 Special or .45 ACP. When the higher power mid-caliber loadings came along (.38/44 and eventually, .357 Magnum), those found a home in the larger frame as well. The .44 Magnum was an easy upgrade within the N-frame's tolerances.
So it really boils down to how long a barrel you want and what kind of flexibility of loadings in the caliber you prefer. Seems to me either a .357 Magnum or a .44 Magnum will do that for you, because you can shoot lighter .38 Special or .44 Special loads in them respectively.
If you like the .357, it's either a model 27 or 28 (same gun with different degree of finish, as noted above). If you want a .44, you should go for the 29.
Whatever you choose, it's going to feel different from the other S&W revolvers you have. Even with a shorter barrel, that's a lot of steel to be holding out there at the end of your arm. But once you get used to it, the extra stability afforded by the extra weight makes shooting even heavy loads easier than you might have thought. And the light loads are extremely comfortable to fire.