I had also tried passive preamps, but found actives to have better bass weight and punch. That is until I tried the Tortuga preamp. I was surprised that the bass equaled or bettered the active preamp I owned (an ARC-REF3) with better, tighter bass, wider and deeper soundstage (with much better channel separation), and more extended & cleaner highs. I ended up selling my REF3.
I also had a chance to compare it to another highly regarded $10k active preamp. The Tortuga's adjustable input impedance feature (2k to 200k on the balanced one) really showed how important it is to optimize the load seen by the source.
By the way, I'm using my current Tortuga LDR1B-V2 (1 balanced input, 2 balanced outputs) to drive a biamped system with a pair of Spectron monoblocks on the bass (25 kohm) and a pair of Double Kronzilla's (with a high speed differentially balanced FET input with 100 kohm impedance). The Tortuga is driving these just fine, still with bass power and punch and pristine mids and highs. The balanced ICs from the Tortuga to the amps are one set of 2 meters and one set of 2.6 meters.
I'm getting a customized LDR3B-V2 with the capability to switch absolute phase on the inputs. All this without a switch or pot in the signal path. I'll be using my current LDR1B-V2 to attenuate the volume of the Spectrons to match the Krons. The Spectrons need to be attenuated by around 4 to 6 dB.