When going active, you'll need an amp channel for each speaker.
If you want to do a 3-way active setup, it's usually going to consist of tweeters, mids, and sub(s). This is probably the most common type of active setup there is.
It is definitely possible to do a 4-way (or more) setup, but you'll need additional amp channels and pass filters for each additional speaker.
Here's a rough example of how a 3-way would be set up:
SUB: LP, 80 Hz, 24 dB/Oct
MIDS: HP, 80 Hz, 18 dB/Oct and HP, 3200 Hz, 18 dB/Oct
HIGHS: HP, 3200 Hz, 12 dB/Oct
Obviously, the frequencies and slopes can be adjusted to the user's preference.