The Buderus LT160 will stack with any size G124X boiler making it the perfect indirect fired water heater option for applications where floor space is at a premium. Depending on how you are controlling your boiler, you may need to purchase an aquastat and pump relay or other controls to coordinate the operation of your boiler for both space heating and domestic hot water, but this is true of all indirect-fired water heaters.
While it does depend on your specific boiler and existing water heater, in general, an indirect fired hot water heater will deliver a higher volume of hot water and recover more quickly than a conventional storage tank type water heater of the same size, and it should do so more efficiently as well.