Ok i got the Xover working and now things are really sounding a lot better. No more drowning of main speakers.
But still need some work, i'm thinking of using a set of High level outputs from the amp to the sub's High level input, which i'll then use the sub's Xover to shape the signal. This way i will be able to control the volume from the reciever.
Because at the moment, i have
PC->Mixer->Sub-(X over'ed)->Reciever
Hence the sub input is fixed and cannot adjust it (well i could use the mixer, but thats not practical)
So the new setup would be;
PC->Mixer->Reciever->Sub
Hopefully this will work, I wonder how "high" the high level inputs will handle, cos i have never done this before.