Bi Amping... worth it?

Yes! It really does make a big difference. Gain matched means that the output of both amplifiers is equal. This way you don't have to worry about an imbalance of power to one driver over the other. Should hear improved sounstage in all aspects. Usually much better tonal quality and inproved bass. Since bass sucks so much juice the seperate amplifier on the tweets really open up the transparency. I'm sure you will be pleased with the improvements in almost all aspects. Good luck

Active crossover sounds pretty invasive to my speakers! More of an upgrade than I thought. And obviously more than just the <$1K than I originally thought.

But what about the passive biamping... JC, is this what you were referring to, when you say it "really does make a difference", or were you referring to the active biamping? I guess the question should be, is PASSIVE biamping worth 1k + associated cables?

Thank again guys... I've learned a lot since stumbling across these forums...

Whatta upgrade boom isn't it Dennis?
First place VTL, than considering bi-amping...!
I can only wish the best in your research.

If you will ask speaker manufacturers they will certainly get "upset" since their buit-in crossover is the best match for the speaker and in some way they're right.
By removing the built-in crossover you will loose the value of the speaker and so you should somehow try and listen first if it's true.
Despite this situation I would really recommend you to ask the manufacturer how would you benefit by removing a crossover and using active bi-amplification.

I also plan to bi-amp with McCormack DNA1 on the bottom and VTL MB100 on the top. From what I figured out I can use it either way passive or active: These amps have both high gain(near 26dB), I will have tubie-sweet mids and highs and fast controlled SS bass doubled on 4Ohm load(my speakers never go that low the lowest is arround 6). The triode mode I will only be able to use in active bi-amplification.

So whenever you will look for passive bi-amplification you should match the gain of amps.

Yes I was referring to passive bi-amping. You will need same amplifiers or matched output gain as you suggested you have. With active bi-amping (more expensive) you will need an additional crossover but this will allow use of mismatched amplifiers. Based on the scenario you outlined above I would guess passive would work well

If you reed specs with no gain specified on the amp all you should do is to derive an output voltage from the following equation:

Output Power = V*V/R (squared output voltage divided by load resistance)

We have load resistance specified usually 8 or 4 ohms and from there we can derive an output voltage.

Than we take 20log(output voltage/input voltage) and get the voltage db gain.

Now there is a question:

What can be the tolerance between two amplifiers for a successfull biamp?
Please, share.