Advice on replacing 12 in woofer in Martin Logan Monolith III's


I'm needing to replace the 12 inch woofers in my Martin Logan Monolith III's.  I am running a dBx 260 active crossover so I can control x-over points and output.   Any suggestions? 
stevepa
I've emiled ML to find out the cubic size,  but who know if they will respond. 

SLS 830669
FR too high for me.

I was told by a mate here in Australia who also wanted them for his Monoliths after he heard mine, that this guy still had the SV12's but he wouldn't ship to Australia.
http://www.highdefjunkies.com/showthread.php?t=14425&s=2374d39826a05548a2cfbdafd2d0c666&p=35...

Cheers George
George do think the ScanSpeak Discovery 30W/4558T would be my best option?  I dug around looking for some SV12's, no luck yet.
You'll have to find what the distortion is like at 150hz and one octave above 300hz to see if as good as the SV12's stevepa, why not get in touch with the guy how's got the SV12's in the above link.

Cheers George