2-Way 3-Way Debate

There are lots of explanations as to which is better -- a speaker with 2 drivers, 3 (or more).

As with any engineering question, the answer is ultimately determined by what you're after. There is an old example from World War II. The Mitsubishi Zero fighter was faster and more maneuverable than the early Allied aircraft. After one was shot down, they discovered why. There was no armour plating in the cockpit to protect the pilot from bullets. Less weight meant tighter turns and faster speeds, but with the pilot more susceptible to injury. Take your pick.

One of the biggest problems in speaker design is the transition between drivers. No matter how steep the crossover curve, both drivers will overlap, giving two source points that will interfere and reinforce each other, depending on the exact frequency.

Crossover points also often occur in the midrange where the ear has its greatest sensitivity and voice and the vast majority of instruments have their fundamental notes.

The more drivers, the more crossover points you have. That's the reason many people like 2-ways and still others are fond of single driver systems. The midrange is very important to them and they think that design type sounds better.

Other people value the strong points of a 3 way (or more) design -- deeper low end, more volume, better power handling and so on. You like your JBLs (which have a very distinct sound to many) so you may not be one of those who values an alternate design.

As far as the audition option, that's not really Audiogon's choice. Individuals selling their used gear are likely not interested in offering "dealer" services. They are selling their gear because they either no longer use it or want to move to something different. The last thing they want is to get something back from an indecisive buyer after they've played with it for a month or two.

I have owned many speakers over the years,and I must say I always preferred two way over three way.

As Mlsstl states, "take your pick."
Crossover points and components involved in the crossovers do affect the sound as do overlap between speakers. Therefore some think simplier is better. However, you will not get true full-range frequency coverage from a single driver, or from most two-ways. When a manufacturer tries to squeeze out a full-range frequency response from a two-way speaker something usually suffers when the midrange driver is asked to cover the top end of it's frequency range or when the tweeter is pressured to extend below it's comfort zone. Even the highly regarded Audio Note AN-E, a rare two-way that is said to operate essentially full range (specified from 18 Hz to 23 kHz at -6 dB; when placed in the room corners) is said to have a "slight cupped-hands coloration," according to John A with Stereophile).
One benefit of small cabinet two-ways is in imaging. Most find imaging to be improved when using a smaller cabinet sized speaker. Some solve the extension problem by adding a sub to a two-way, but this is not ideal as most think two subs (or more) are better. When you start adding subs, the question becomes "wouldn't it be better to simply purchse a full-range speaker?"
Regarding crossover slopes, a few very highly regarded speakers use shallow first-order crossover slopes, such as the outstanding Venture Ultimate Reference reported on in this month's Absolute Sound. However, the majority of manufacturers choose steeper slopes that allow the drivers to operate in their optimal frequency range.
Personally, I would use smaller two-ways in a smaller room, and then add a sub or two since it would be easier to adjust and integrate the bass response when using adjustable subs. I choose to use larger near full-range speakers in a larger room.
Like many things, there is no "right" answer. I would first think about the room size and where you will position the speakers within the room, and second about the amplification you plan to use - high or low power, SET tubes or a 500 wpc SS amp. The amplification (and matching sensitivity) significantly affects the sound of the speakers to the point where you might never hear what the speaker is capable of when powered by a mismatched amplifier. Finally, I would go out and listen (with the type of amp you will be using) since no one design feature will solely determine whether a speaker sounds good or bad.