Any experience with Northcreek crossover for B&W?

Does anyone have experience with the Northcreek crossover upgrade for the B & W 801 Series II speakers (or any other B&W model)? If so, was the upgrade difficult to install and was the sonic improvement worth the $1600 cost? How would you describe the sonic improvement? Trying to upgrade from my B & W's can really get pricey and this appears to be a reasonable alternative. The amplifier in use is the Pass-designed Threshold S550e and the FET 10 preamp. The SACD player is the Sony SCD777ES. Thanks.
I have the 801 III with the North Creek's and I feel it will get you as close to the Nautilus without breaking the bank. Before the Nautilus it was the only way to get past the weakest link. It was fairly simple to install and will take a couple hundred hours to break in. The bass was not quite as deep at first for me, but the mids and treble really open up and are more musical. I still like my Matrix III's w/North Creek's compared to the Nautilus. The crossover was their weak link considering it weighs less than a pound and has sand cast resistiors, etc. The north Creek's are a quality component and essential in getting the most out Matrix series and knowing it's potential. If you go for them, I would bet you won't go back. As you already know they will require great front end components.
The Northcreek literature indicates that their crossover upgrade eliminates the protection circuit. What does this mean in practical terms? Will sharp transients (accidents happen) or prolonged loud volumes (not a problem with me)damage the speakers? Thanks for the comments.
I think at the time they said they were over protected or something to that effect anyway. They will answer any questions at North Creek, they were great when I bought mine. I will tell you that with my Krell KSA-300S I have used since I bought mine 5 years ago and immediately modified them. I have never had a problem with any possible mishaps and they seem bullet proof (within means) and have never been a problem.
I know two Matrix 801 sIII owner's using the North Creek crossover. They both seem very pleased with the results.
Thanks for the helpful comments. My NC mod purchase will move rather slowly but I will certainly share reactions when it takes place.