Biamping, bass and amplifier type.

I've biamped in just the way you're considering: a ss amp to the bass cabinets of my vr4 iii's, and dynaco mk iii monoblocs powering the mids and trebles. Though my ss amp puts out 170wpc, and the Dynaco's are rated a 60w, gain difference is not an issue b/c of two convenient configurations in my amp and preamp: 1) my ss amp has volume pot (per channel, but a single pot controlling both work just as well); and 2) my preamp has two sets of outputs. Those aren't requirements by any means, but it makes bi-amping a cinch. I keep the volume pots on ss amp at about 4, and then leave them alone; everything is controlled via the preamp, and I don't notice any imbalances across the volume range. And with the VRiiis, which get down to about 20hz, no subwoofer need apply.

I disagree with Stewie. He's gotten lucky with gain. Many amps will increase at different rates. Some amps will double output with a quarter turn while other only go up 10%. There is no way to compensate for different rates of gain.

There are 2 main types of potentiometer. Linear and Log.
They both may start (50kohm, say) and End, (zero, hopefully) but get there in 2 different ways.....'slopes'. They will only match resistance at those 2 points based on rotation.

As for bi amping, I have never heard a discussion of amp latency....that amount of time a signal takes to go THRU the amp. If it took JUST 1 millisecond longer for the signal to go thru the hi frequency amp, that would be like pushing the mid/hi drivers over 1 foot back. (away from listener)
This would start no end to problems.....smear of image, phase problems and more. The holocaust at/near the x-over frequency would be awful.

Before you toss this one in the round file, think about people who are good enough / discriminating / well eared enough to hear which way a fuse is installed.

My speakers are bi-amped. I run out of my preamp into a dbx Drive Rack PA. From there I go to a JRDG 102 amp which drives compression drivers through horns. The other amplifier is a Perreaux PMF 1850 driving 15 inch JBL woofers. Since the drivers are so different, what would be gained by using identical amps?
I gather that most of you are talking about using the inboard passive crossover for bi-amping. Is that correct?

You might want to consider a Drive Rack instead. Just bypass the native crossover and hard wire your drivers to the respective amps. Every parameter can then be modified by programming the dbx including time delay between drivers. There is a learning curve but if you like to fiddle around with your equipment, this device will open the door to infinite possibilities.
I got mine from Amazon and the price was very good. The pros advised me to go this way rather than Behringer.

Here's something from Albert Von Schweikert posted
on the Von Schweikert board at Audio Circle. It may answer some questions, or raise new ones. In any case, the full discussion can be found here:
http://www.audiocircle.com/circles/index.php?topic=59529.0

From Albert Von Schweikert:
Hello Fellow Audiophiles,
Over the past 32 years, I've used bi-amping as a method to achieve more realistic sound quality. A decent, high powered solid state amplifier will give you explosive and tight bass power, while a smaller tube amp will give you the "air" and image float you are seeking from your sound system. Here are a few tips:
1. The bass amp does not have to necessarily be expensive, but make sure it has a large transformer and power supply to ensure "tight" bass. All of our speaker designs employ 4-ohm woofer systems, with a dip down to 3.5 ohms, so make sure the amp is stable into a 4 ohm load. Power requirements depend on your room size and how loud you want to go. I suggest 200-300 watts per channel if you have a large room and want an explosive dynamic range.
2. The tube amplifier can have as little as 20 watts per channel in a small room, but in a large room, you may want to have 50-100 watts per channel to avoid clipping at high volume levels. Due to the distribution of power over the frequency range of 20Hz to 20kHz, you can use a much smaller amplifier on the midrange and tweeter module. Use the 8-ohm taps on the tube amp, but feel free to experiment - it won't hurt anything to try other taps.
3. The "secret" to achieve "killer" sound quality is to ensure that the amplifiers have exactly the same input sensitivity. The amplifier with the lowest numerical rating, i.e. 100mV is much more sensitive than an amplifier with a rating of 500mV - the higher the number, the lower the sensitivity. You'll need to reduce the higher sensitivity by using a series input resistor. This can be installed inside your amplifier, directly at the RCA female jack leading to the input stage. If this sounds a little scary, then build an adaptor to house the resistor outside the amp. If you contact Michael Percy at www.percyaudio.com, he will advise you on what you'll need to get from him. Usually, a female RCA jack, a male RCA plug, a high quality metal film resistor, some plastic sleeving, and a short piece of high quality hookup wire is all that is required. Basically, you're inserting the resistor between the "hot" connection from the female RCA jack to the male RCA plug, and then using hookup wire to connect the ground leads. The entire assembly can be only a few inches long and installed into a plastic or Teflon sleeve to prevent short circuits. This adaptor is inserted into the signal path between your preamp and the most sensitive amplifier. As you can infer from this description, the adaptor is used in between your interconnect and the input jack of the amplifier.
Michael Percy sells these parts for less than $100 for everything you'll need, and he'll also help you select the proper value of resistor to match the sensitivities. Although this simple technique may sound like a "Micky Mouse" setup to "sophisticated" engineers that design chip OP AMPS and sell electronic crossovers to the PA industry, it is a very "pure" form of passive matching that will stomp the crap out of any electronic crossover I have ever tried.
4. Brands and Models: basically, put your money into the tube amp, since even inexpensive solid state amplifiers have stiff power supplies and enough quality to drive woofers with high speed transient response, high volume levels without clipping, and tight bass. Twenty years ago, Adcom built a 200-watt amplifier for around a thousand bucks new, and half that price used. Today, there are many expensive amplifiers that sound great, but you're paying for an expensive chassis, face plate, branding (advertising), and so forth. Instead, look for an amp with a large transformer and high quality power supply.
Tube amplifier choices abound, at all price ranges. Some of the best values are from China if you are on a budget, but large American tube amps from long established companies will be a good investment, with good resale value and the ease of repairs. Don't worry about the availability of tubes, they're going to be around for another 50 years or more due to the ever-expanding market for tube amplifiers.
Happy Listening from Albert Von Schweikert