engine joe said:
no, i meant active crossover. how good can the power supply, amps, and crossover be in a low budget monitor in comparison to a passive monitor and external amp?
Probably not a big difference there. Passive crossovers generally require heavier components - which in turn cost more, due to the amount of electrical energy they have to handle.
The real matter with biamp vs. passive is efficiency. This manifests in a few different ways: first, passive crossovers waste power & generate heat. The raw power coming out has to be split between the drivers, which is basically done by splitting the signal in two, then shunting off the high or low frequencies before they go to the driver.
This means that your amp will have to work harder just to reach the driver's rated capacity - if you have a woofer & tweeter, each rated for 50 watts, a 100 watt amp will never deliver 50 watts to each component because of the filter network.
With an active crossover, however, you divide the low-voltage version of the signal, which then feeds 2 separate amps. These amps then power the speaker directly, and can give their full power output to the driver.
Another benefit of this comes from the fact that low frequencies use far more energy than high frequencies. Consequently - I'll cut to the chase here - if you're driving passive speakers really hard with a lot of bass-heavy music, your high frequency response (that is riding piggyback on the same amp) is going to suffer.
With active crossovers, bass energy goes to the bass amp (which is often a more powerful amp) and high frequency energy go to its own amp - so, no matter how hard you push the bass, it won't mess up the highs.
There's a good explanation
here (Mackie.com) - read between the sales pitches for their HR monitors

and the technical explanation is quite good.
I was just in the same boat, monitor-wise. I opted for (and am awaiting delivery of) a pair of Samson R5a actives. They have ribbon tweeters, and from my research they have gotten several good reviews, especially bang for the buck. If anyone's interested,

I'll post my impressions after they arrive.