Great if you are using a public address system for your listening pleasure....
If that is what you are using for speakers, then that particular Crown series should do a decent job, since they are designated as PA (public address system) amps.
I had a 400 watt biamp made by Kustom (300 watts for bass, 100 watts for treble) to power a pair of Altec A7's for my band in the 70's (huge improvement on the Peavey powered mixer it replaced). So what exactly is new? Also, it sounded great for its time. Now I use a current model 700 watt QSC to power a couple of passive Mackies for solo gigs and other live stuff...it sounds better. Use any of the above in my hifi rig? No. Set it up to scare kids on my porch on Halloween? Yes.
Often you get what you pay for...
I tend to agree with Ms. Liz. When I was a young man, I thought that if I used the pro stuff at home, I would have an awesome stereo. It was until I got introduced to high quality sound equipment. If pro sound equipment floats your boat, rock on brother!!!!
Another thing you are missing is that the built-in passive crossover of quality speakers is more complex and less "textbook" than what these amps provide. Those crossovers are designed to suit the needs of the specific drivers in the specific enclosure and you cannot implement their transfer-function without careful measurements and filter design.
True biamping, done properly, is not as trivial a task as you have described.
After agreeing with Kal, my first question would be: What are you biamping?
If it's a 2-way, the passive at about 2KHz probably isn't as "awful" as you think and an "off-the-shelf" active crossover can be just as bad or worse. Besides, the power required above that is minimal. Ribbon tweeters usually require passive filters or, at minimum, a capacitor for protection.
If it's 3 (or more)-way, and the crossover is below 400Hz, active biamping becomes more reasonable. It's when you get down to 100Hz, and the inductors start looking like toroidal transformers, that active biamping really pays off. The problem with that is all the passive crossovers in the speaker are usually on a single PCB.
You're on the right track. Get rid of the nasty passive x/o, but converting a passive speaker may be a bigger job than you think to do it correctly. Do your research, know what you're getting into, then dump the passive x/o and enjoy the results.
Also, biamping home stereo speakers is an insult to all those brilliant speaker designers who slave away at making great crossovers.
I would buy a real power amp first. Why bi-amp something like these? They give a power rating at 1khz only. That way, it sounds like a lot of watts. Who listens to just 1khz? True amps give the rating at 20-20,000 cycles. What happens to these amps when you run the full 20-20,000 through them? Half of the power rating? Worse? If you get a real amp, you might not have any reason to bi-amp it.
If you use exclusively digital sources, I'd say that the answer to both of your questions is "yes", but not via the route you describe. Crossover units operating in the digital domain provide a bi-amping solution that is immensely effective. You can spend a lot or a little, and set up can be complex or "push button" simple.
Either way, I'd argure that it's "cheaper, easier and more effective" now than before.
Like it was mentioned by other posters above.
These amps are cheap, and made for band with tight budgets to get by, otherwise they may not be able to perform.
Kr4 said it is very complicated. It definitely is. The audio reviewers probably would like to get more for their money, than they put in their systems.
Do you have access to the expensive test gear like they do to see the results from doing this? Beside sounding bad, it's easy to damage the drivers also.
Yes it may be cheaper to do this, but with digital noise added if you go the digital route.
Active adds a lot more parts than passive does. That means more money spent for more parts, and more noise.
In the end, it's hard to out do the builders that have the expensive test equipment, and are able to do a lot of trial error to get where they are. That's why I gave up trying to get more for the dollar years back. A lot of us has been there.
My answer to your question is that while there may be cheaper and easier solutions available, the best sounding approaches to bi-amping are neither. IMO.
I use QSC 500 watt/ch amp for my bass horns, <100 Hz, but my Marchand xover is much better sounding than the built-in on the amp when it comes to evaluating what comes out of the mid and tweeters. (BTW, I actually prefer passives for the mid and tweet crossovers in my system. YMMV) Remember, everything goes through that circuit on the amp, not just the low end, and as others point out it wasn't built to audiophile standards.
Still, the amps are built like tanks for the use we might put them through in home systems. If I didn't already have a Classe 301 in my theater for the mains I would consider using a QSC amp for that application as well.