... and last but not least.. You do realise what the issue with the M41's is?
There was no room on the backplane to add in a vectoring module.
For those who don't understand what I mean its like the equivalent of say sticking a sound card into a PCI slot into a PC, but if the motherboard on your PC only has 2 PCI slots and you already have 1x Network card & 1x modem card in it, then there's no room to add the sound card.
At one time ECI had detailed specs on their site of the M41 & V41 which has now gone, but from memory the 2 DSLAMs were almost identical except they jiggled things around a bit to make room. Its a long time ago since I saw the photo's and my memory could be wrong but they seemed to have turned some of the internal parts sideways on the left to make more space to add in another slot which could take the Vectoring Engine card.
The Huawei's have a spare slot so that inserting a Vectoring engine module is no big deal. Bang in the Vectoring card, configure it and away you go.
The ECI-M41's could actually do Linecard based vectoring because of the VTU-C64's, but line card vectoring isn't as efficient as system level because you can end up with wasted ports on the linecard. The Vectoring engine card which is slotted in controls vectoring on all the ports.
There's a discussion
here on System Level Vectoring -v- Linecard (board) Vectoring.