What else do you already have? Or is your D01 your first and only brush? Do you use mainly soaps or creams?
It might be fun to branch out into something completely different. A Rooney, Simpson, Plisson, Kent or something..?
That's funny, my current stock as of today:
Shavemac DO1 23/48
Shavemac Silvertip 28mm
Shavemac Silvertip 30mm
Simpson's Chubby 1 Best
Simpson's Chubby 1 Super
Rooney 1/1 super
Rooney 1/2 super
Rooney 1/1 Finest
Rooney stubby 1
Rooney stubby 2
I think that's it for now.