CAN Bi-Amping been done Correctly?

I have a pair of B&W 802 series 3's that are bi-amped with a pair of Parasound amps. The difference was nothing short of amazing.

I don't know if it can be done "correctly", as I don't know what "correctly" is. But if you are asking, if you can have glorious sonics, by bi-amping Martin Logans, yes.
I use Curcio modified MKlll's, on the panel, and solid state, on the bass. With 60 watts, on the stats, and 200 watts, on the bottom, I think it sounds grand. The Martin Logans are Sequel ll. I did a lot of interconnect cable, and speaker cable swapping, before arriving at what I liked.

I work with pro sound reinforcement a lot and multi amping is a way of life. Use a big solid amp for the bottom and you can get away with a smaller amp for the highs and mids because the big power suck is the bass. I don't know why you would need the same amp for highs and lows, especially if you are mixing two different speakers, though you may need to experiment to find an amp combination that suits you. The difference i see in the pro side verses what i see here is that we use a cross over to split the signal out of the board (i.e. the pre-amplifier) where as it seems that in hi-fi applications the full range signal goes to both the mains and the subs with a cross over in the sub controlling what the sub reproduces. The mains are also trying to reproduce that low signal and that may be where the clash comes from...just a guess. In pro set ups you also need to tune the cross overs and eq for the room, it's not a simple plug and play operation. The cable swapping noted above seems to be a dialless method of EQing the system.

Yes!

I have used a tube amp for mid/trebble (passively crossed over), mosfet monoblocks for bass and a bridged mosfet stereo amp for sub, the 3 lots of amps being crossed over electronicaly.
I have used a professional x-over with the resistors and caps swapped for better ones and better op amps also installed.
It sounded pretty good standard and exceptional modified.

Realise that pro electronics are usually better designed and built than hi-fi, unless you are looking in the Krell/Levinson bracket.
It has to be. It gets a hell of a life, both thrashed and shaken. Needs to be able to survive torture tests hi-fi never sees.
Also needs to sound pretty good, mid and high frequencies are usually taken care of by horn drivers - and say what you like, but they are revealing enough to make shoddy electronics horrifically noticable.

Pro x-overs can often be found quite cheap second hand and the only big hassle is using xlr connectors (ballanced) in a single ended system (assuming yours is).
Most can be switched so the output is unballanced with pin 2 hot, pins 1, 3 and the shell cold. Just means a bit of soldering to swap connectors on your interconnects - not very difficult.

I chose a x-over that was internally unballanced and then stripped out the op amps and circuitry that did the ballanced to unballanced conversion. Sounded a wee bit better. I could of changed the xlr connectors to rca's as well - but I've yet to be told something good about rca's! Wrong connector for hi-fi, that is for sure.

The other good thing about pro gear is that they don't make a secret of the circuit diagrams - helps doing mods no end. In fact, the user manual for my one had the circuit diagram in it.

Perhaps the only downfall with some pro x-overs is that they are designed for lower end systems and they invariably use a wall wart power supply.
Best to avoid these, look for one with a fully internal power supply, it will most likely be quite nicely regulated and that helps.

Don't be put off by the fact that you have to set the level for each frequency band with a knob (usualy seperately for each channel).
Your ears will soon tell you when you have it right. Most people start off with too much bass. Take your favourite recording to other places to listen and compare. Accoustic and vocal music is good for set up. Get everyone from the barratone to the soprano sounding good and you'll be real close as we all know what a voice should sound like!

Best of luck, NOTHING beats a good multi amped system in my oppinion!