Is Bi - amping worth the trouble?

Blindjim,
You're welcome. I'm happy to hear that you find me helpful.
Passive bi-amplification amounts to sending the signal from two amplifiers into the speaker's passive crossover and, unless lack of power is an issue, does not differ substantially from bi-wiring.
True bi-amplification places an active crossover between the preamp and the power amps, sending the portion of the signal that you assign to each amplifier and subsequently to each driver (or driver set). An active crossover will normally afford much more flexibility by allowing you to alter and adjust X/O points (frequency cutoff), crossover slopes (db/octave) and increasing or decreasing relative gain.
It also does not usurp a large portion of your amplifier power as the passive crossover in your speaker will.
I am not very familiar with VS design but I'm sure I've owned something like them in the past. Unless they provide you with a way to completely bypass their internal crossover, they are not setup for true bi-amplification and the advantages it affords. Please remember that much of the advice you receive from dealers, the factory and even certain, if not all, reviewers is driven by marketing interest. This forum is a good, neutral source of info but you need to be aware that at least some of what you read here is the well-intentioned echo of the aforementioned marketing people.

As a cost saving measure, remember that when you bi-amp, you need amplifiers of far less power to achieve the same loudness and headroom. With Magneplanars, I was unhappy with a 35 wpc tube stereo amp, but fine with two of these, passively bi-amped (AKA dual-amp bi-wired). So, I could concentrate on fine quality amps, but not necessarily high-power fine quality amps.

Oh, I have a couple more comments: don't bridge! Bridging an amp compromises its technical performance, and I have heard the degradation. If you decide to use one stereo amp per speaker, bi-wiring the two channels separately with a Y-connector up-stream (AKA passive bi-amping) is MUCH better than bridging. To say that "its not worth it" is not in the spirit of high-end audio. We all know that more fussing and more money brings about only incremental benefits. So, if a difference is definately audible, then the reward is achieved.

I dont really see the point of biamping if you are using the same amps, I have done it and the difference was really minor, go tube for the upper range.

Yes the best Ultimate way to Biamp is to open up your speakers and pull the XOver out and wire each driver directly, remember you then have to use 3 amps, one for each driver that is woofer, mids and tweeter, wait you have two woofers there make that 4 amps! While your at it change the wire going into each driver and by the way add some blue tack to the frames of the drivers. Leave the wire long enough so you can hard wire directly to the amps terminals. Do use silver wire for mids-tweeter and copper for both woofers. You can also use different interconnects from the active XO to each amp, I would recommend Nordost for mids and tweeter amps and Siltech for the bass amps.

Of course you can start slowly and enjoy each step of the way! No other system will sound better to you.

I would start the easiest and cheapest way possible, see if I like the changes and do some more. Say get a nice tube amp, there is a new Genesis amp push-pull with 6550 tubes that I think would sound wonderful, it was designed with biamping in mind, or say a McIntosh 275 or 240 amps. and just "dual-amp biwire" it, If you like this for the amount of 2 bucks you can make a passive line level XO, which is what most gung-ho biampers recommend (check the Oris speaker website) some say first order is the best (Romy the cat). Before buying an Active Xover I would probably change the values on the tube amp coupling capacitor and resistor to avoid low freq. this would be the most purist way to do it (I have done it) you also avoid another set of ICs which is not only expensive but detrimental to sound (not to mention the damage an active Xover will bring to the system) Now for the tweeter amp the line level Xover didn’t really worked all the way up, the best thing there would be to add a cap between the tweeter and the amp (Hovland?). I would use the active Xover for the bass amps, there is where the passive original Xover does the most damage! Those huge caps and huge inductors are no good!

Be brave and do it!

If you can run Solid state on the bottom with LEVEL controls, which many do not unless running a pro audio amp than you will have difficulty matching up gain with a tube amp on top.. YES there are still benefits of running 2 of the same amps in a verticle bi-amp config, this is because you will still have dedicated Current running to just the bass drivers not sharing it with the upper end. However it can be as explained here to some more accurate degree very little advance, unless it is just the right amp speaker combo it could be substantial even in a passive crossover system. The VK 500 you have in question is a Dual mono with dedicated power supplys to each channel I believe, so Having 4 Dedicated transformers, with Hi current and Higher Capacitance per channel can be better even with the same 2 amps... Also, I totally agree that DO NOT bridge and expect better results, the Verticle bi-amping with 4 channels should prove to sound better anyway, but you could experiment both ways if you have the amps that can bridge in the first place.