Plenty of good advice from the replies. Here's another suggestion that may offer a more simple solution.......
Check out the Outlaw ICBM. It's an active crossover that offers adjustable XOVER frequencies. It is placed between the preout and main in. In addition to many outputs for multiple speakers it also has 2 outputs for subs. So, there's no need for y adapters from the preamp.
The ICBM has been out of production for a while but can be found in the used market. It originally sold for $250. May make your hookup more simple.
Another mention.....do your 901's have a lot of age on them? If so, check on the condition of the foam surrounds. I've been down that road.
Check out the Outlaw ICBM. It's an active crossover that offers adjustable XOVER frequencies. It is placed between the preout and main in. In addition to many outputs for multiple speakers it also has 2 outputs for subs. So, there's no need for y adapters from the preamp.
The ICBM has been out of production for a while but can be found in the used market. It originally sold for $250. May make your hookup more simple.
Another mention.....do your 901's have a lot of age on them? If so, check on the condition of the foam surrounds. I've been down that road.