I think your gear may be working just fine. The problem is that biamping and using the crossover is just not producing a good result for you.
The first problem is that a biamp system is a good solution for full range sound sources (recorded music, keyboards, drums). Your bass is, uh, a BASS instrument and doesn't have so much high end output that the upper split has that much to do. The low E fundamental is 40Hz; an octave higher is 80Hz, the fundamental of the highest E you can play on the G string is 160Hz. The first (octave harmonic) of that high E is 320Hz and even the third harmonic (the next octave is still only 640Hz. With the crossover frequency dropped down to the lowest range (70Hz) you'll find that only higher notes will be routed to the 2x10 cab and, simultaneously, you'll be robbing the 1x15 cab of most harmonics and many fundamentals. By the time the crossover freq is up to 12 o'clock, pretty much all the signal will be sent to your 1x15 and your 2x10 won't have much to do. This is not to say that there's not much bass business above 1000Hz, but if you're not slapping or playing with an extremely bright sound, there probably won't be that much going on.
While the crossover is splitting things up possibly in a somewhat non-useful fashion, you're also suffering an enormous power loss because of the biamping. I don't know which amp you're using, but what's happening here is that the low-end channel is being fully used but is only driving one speaker now instead of two. The high-end amp is mostly not doing anything because of lack of program material, so you've effectively lost that amp power as well as getting no acoustic output from the 2x10 cabinet. As opposed feeding both channels with a full range signal, you've lost 50% of the amplifier power and 50% of the speaker area of your rig - that's only 6dB, but a very significant loss.
On top of that, in your original setup, you were running the power amp in bridge mode. When you couple the amps up in this way, it acts as though the impedance of the speakers was reduced by half. Numerically, that is a 2x increase in amplifier watts (again, another 3dB). And in practice, it's probably even higher than that since you were probably running the two cabinets in parallel which would again double the amplifier power!
All those splits are costing you a lot of perceived output and that's why things sound lackluster.
Biamping is really useful when you have the right circumstance. If you have a full-range (bass to high treble) signal and you want it to be really loud then this is a good application. The problem with amplifying a piano, synth, or even voice is that the best speaker for high frequencies is a small one which can vibrate faster and the best speaker for low frequencies is a large one that can move a lot of air. But the big bass speaker is too massive to reproduce highs and the tweeter will melt down if you try to drive it with high current bass signals. So, you split the signal with a crossover and let each speaker do it's own specialized job. For a bass rig, there's not that much for the high end channel to do, and a 2x10 cabinet is too big to reproduce the highs well anyway (2x10 might be a gutless low end cabinet for us bassists, but it's bigger than most woofer in most full range systems).
So, if I were you, I'd switch back to your original setup - bridge the power amp, feed it with the full range output from your F1-X, and run both speakers full range and parallel. You'll probably be a lot happier. If you want a little more flexibility, then run the amp unbridged, feed both channels with the full range output, and you'll be able to use the gain controls on the amp to control the balance of the two cabinets independently.
You can verify that the crossover is working properly, but feeding it with a full range signal (e.g., your iPod or the like). You'll hear that the 2x10 is plenty busy then, although you may not like the sound of your rig vs. something with flat response.
The crossover (whether passive or active) doesn't just protect the tweeters from getting cooked. If the tweeter could take the power and you fed both speakers with full-range signal, you'd find that there would be certain ranges where both speakers were actively able to reproduce the sound. The sound in those overlap areas will be terrible, because the time response of the speakers won't match (the woofers mass will blur transients for instance). When you have time shifts and blurring like this, you get phase cancellation which can make things thin and/or honky sounding. If this is in the midrange, where human hearing is the most sensitive, it will make for annoying sound. The crossovers divide up the spectrum and reduce these problems, and a properly designed system is tweaked for good results in the overlap areas. Your F1-X crossover doesn't have the adjustability to make these sorts of compensations. In fact, these sorts of adjustments are exactly what all those weird trimpots are tweaking in Ron's ELF Integrator.
I hope this helps. Having all the fun/advanced stuff is cool, but often the simple setup will yield the best sound.
David Fung
