I have play with 1500Al, 1500Al-1, 1501Al-1, 1501Al-2, 1500Fe, 1501Fe, 2216Nd woofers so I think at I know pretty well how they work
I did not say at 2251j/251j were better than 2123H, I have not play with 2123H yet, I own two 2123H baskets and C8R2122H recone kits that would be interested to try
Ari