Well, I was using the Darkglass X7, which has built in low- and high-pass filters...
Don't get me wrong - they did sound good, but I never got it to sound as good as when driving an amp and cab.
After a lot of soul searching, I recently bought a Sunn 300T amp, which literally has all the features I want from an amp. Separate and blendable channels, graphic EQ and compressor. IMO the best sounding all tube bass amp in existence. I had a brief stint with an Aguilar DB 751 before buying the Sunn. Fantastic amp in every single regard, but in the end a bit too clean for the tone I was looking for. I'm pairing it with my Epifani UL410 (best 410 I've ever played), rated at a 1000 watts, with great efficiency. Gonna record with a Radial JDX48 and micing the cab up.