I have successfully used the DriveRack dbx PA2 LMS (loudspeaker management system) with vintage gear and some modern speakers. It works quite well as an external xover for 2-way and 3-way speakers and is affordable. The only downside is that it requires some time and patience to setup and it looks like Pro gear (which it is) and not home audio gear. I mount it backwards in my audio rack and it's practically invisible.
Audio Nirvana published a great article about restoring vintage Altec Lansing Model 14s and described how they used this box to overcome some fundamental design flaws of the 14s. I followed their recommendations and it works great. Here's a link: dbx DriveRack PA2: The Future of Audiophile Systems
Although I don't find external EQ and xover to be necessary in most situations it has always improved the sound of whatever speakers/rooms I have used it.
Audio Nirvana published a great article about restoring vintage Altec Lansing Model 14s and described how they used this box to overcome some fundamental design flaws of the 14s. I followed their recommendations and it works great. Here's a link: dbx DriveRack PA2: The Future of Audiophile Systems
Although I don't find external EQ and xover to be necessary in most situations it has always improved the sound of whatever speakers/rooms I have used it.