Passive bi-wired to active, bi amped, undoubtedly. The ninkas are two way, and both bass drivers are identical, so you really only need two amplifier channels to go active. If you really wanted to, you could use a third and power each of the bass drivers with its own active amp channel, but the big gain is from passive to active. Going from active bi-amped to active tri-amped in these speakers would be similar to the improvement from bi to tri amping them as they are.
FWIW I also have a mainly Linn system, and started out with 5140s singly amped by a 5105, then over time move to bi-amped, tri-amped and finally active. I can tell you beyond a shadow of a doubt, the biggest change was going active!! Adding amps did help some, but the difference after going active was amazing! The bass was so much deeper and tighter, the highs had more air, they almost sounded like different speakers!
If I where in your situation, Id go the bi-amped active configuration, its just the most efficient improvement you will make. A word of warning though
.. give the active cards a while to burn in!!!! When I first did it to my 5140s I was really disappointed, the highs where rough, the bass boomy, basically the speakers sounded WORSE initially, once the cards burned in, the sound just kept on getting better! I loved it so much, I have the center and surrounds active as well! If you use a 5125, you would need two stereo cards for the ninkas, and you would still have the mono amp channel left open.
Ken
