Do I need another amp for a sub-woofer?

[Alien Mantis]

If your 4-channel amp has line-outs, use them to connect a little Class D monoblock amp for that Bazooka sub.

You don't need an EQ, because the monoblock has a built-in crossover.

If your 4-channel amp does NOT have RCA line-outs, just use a "Y" and tee-off from your RCA's coming out of the LOC.

Does that 4-channel amp have a built-in High Pass Filter?
( hopefully it does )

Set the HPF crossover on the 4-channel to 125hz.

Set the LPF on the Class D monoblock to 100hz.

Balance your gains. Don't push that sub gain too hard on the monoblock.
It is not a volume knob.

BALANCE everything. And what it is.... is what it is.
If you need MORE bass, you will have to redesign your low-end.

That Bazooka tube is not going to give you alot of bass, but it will help round-out your lower-end some. Just don't expect a miracle, and you will be satisfied.

I don't know the specs on that 10" Bazooka off the top of my head, but I am guessing it might be something like 250watts RMS at 4ohms.
A Class D mono amp around 300 watts RMS @ 4ohms should be fine.
( might set you back around $100 or so )