Passive vs. Active sub setup/external crossover/EQ

Regarding proper setup of a passive sub for the best sound: Do I need a crossover or EQ? Can I drive it directly with another amp? Currently it's hooked to both the L&R speakers and L&R amp outputs, as proscribed in the diagram on the bottom of my sub. I've placed it about 12 feet from the left speaker. The sub has 8 clip posts as powered input. No RCA or other signal in.

Here's my system: Paradigm Titans and Paradigm SB 100 passive sub. Sumo Polaris 310 stereo amp, Sumo Athena pre, Proton 440 tuner, Rotel 955ax CD, vintage 70s Pioneer 'table with Pickering pickup, AudioQuest cabling.

I listen mostly to the Blues, Jazz, Acoustic/Vocal, Classic Rock, and Classical, in that order.
If I understand correctly, you are running both the L&R speakers full range as well as the sub.
Suggest you get a Paradigm x30 active crossover. Put it in your system AFTER the pre-amp. Get another acceptable amp, (a monoblock 1-channel is all you need) and drive the passive sub with that.
You'll be connecting the line-level low freqs off the x30 to the sub amp and the line-level high freqs to your sumo Polaris 310.
This setup passes the low frequencies to the sub and the higher freqs to your Titans. The low end is adjustable and your have 2 or 3 (I forget) choices of your crossover point for feeding the Titans.
The x30 is usually available here used for $125 and the amp choice for the sub is up to you.
Good luck and hope this helps!

Myraj: That is correct, they are currently all full-range. Thanks for your input. Looking about, I see Energy also makes an active crossover, anyone have any experience with it?