My current alarm Guardall Rascal Super is broken so needs replacing(we are using 4 programmed zones and chime). I'd like to replace the control unit unit and bellbox but use existing wiring, sensors and internal speaker. I'm looking at the MDT Avanti 8 and AG6 bellbox (current bellbox looks tatty and has no strobe).

1. Is the chime quite loud? We would like to hear if someone enters the house from the other side of the building.

2. The Rascall Super system is 12v and I think the Avanti 8 is 13.8v, will our existing sensors work with the new control unit?

Most alarm accessories are interchangable , and your choice of panel and bell will work with your existing setup.I personally would use a Texecom panel and bell , the instructions are very easy to follow.