Location of fronts and neighbours

Have a chat to your newneighbours.
Tell them about your concerns and let them know that if it is too loud, tell you and you'll turn it down.

I would suggest that the sub should be as far away from the joint wall as possible, and with the speakers fairing way from the wall will help, but the overall sound pressure level is what will annoy the neighbours.

Darren: Here is my experience - no easy solutions, I'm afraid.

My wife and I were involved with the design & build of our new house.
It is timber framed with blockwork outer walls. We fitted the partition walls using a dense plasterboard and filled cavities with dense rockwool. In my judgement this didn't produce much improvement. We also laid expensive dense rubber under the underlay & carpet in one bedroom to improve sound from the kitchen below. This didn't do much if anything.

What did work was that we built a secondary partition wall which was only attached at the ceiling & floor. The cavity( about 7.5cm was left empty) both walls were filled with rockwool. In total we lost 20cm floorspace from one dimension. This was amazingly successful and prevents noise from the Hi-Fi being heard in the adjacent bedroom.

The solution to noise transfer from above/below I believe is similar - construct a 'floating' ceiling about 2-3" below the existing. Special fixings decouple this from the original ceiling.

All of the above applies to our timber frame house where, in my experience, most sound transfer is through the wooden joists. We helped build a brilliant house but sound transfer from room to room was a failure except for the room with the secondary wall which a great success.

I don't believe there are any magic products, no matter how expensive they are. but decoupling walls works.

Sorry for the long ramble but you can probably guess that this failure still annoys me 12 years on.

Marsh

After my horror at the demise of a GX100 (like mine!) my general advice echoes Kevin's, be good neighbours. My semi-detached neighbour and I observe a 10pm curfew on loud music/movies and DIY.

On soundproofing, I'd echo Marsh's advice. Our isolation installs at work are effectively freestanding inner walls (plaster over ply sandwich) and almost air tight. The rockwool fill turns an impact on outer or inner wall into thermal energy to minimise transfer of pressure to the opposing wall. My best example is the spaced quadruple glazing in our nightclub in a town centre hundreds of metres from housing. That uses a floating trim around the cavity, with rockwool behind. Be aware that low bass will be attenuated least and needs significant mass to stop/absorb it.

Try to minimise the sub-bass, this may be a time when corner positioning of the subwoofer isn't a good idea. And avoid mounting speakers on the shared/party walls so the opposite wall may be better.

Hope this helps.