Lew, I think Roger Modjeski (who designed the electronics for Beveridge) has an updated/improved x/o for the 2SW, as well as a new dedicated direct-drive tube amp for the speaker.
I had the Dahlquitst DQ-LP1 for years, selling it only after I got a First Watt B4. The B4 is unbelievably versatile: high-pass and low-pass 1st/2nd/3rd/4th-order filters in 25Hz increments from 25Hz to 6375Hz. All discrete (Toshiba Jfets), no opamps or IC’s. Unfortunately, the B4 is no longer available assembled, only as a DIY kit. Nelson’s Pass x/o is even better, but sells for a lot more (the B4 listed for $1500).