I'm replacing my boiler while extending my house. Simultaneous hot water draw off from multiple points (eg 2 showrs going at the same time)is a priority. The extended house will have a main bathroom and two en-suites. My mains water flow rate is approx 20 L per minute (don't know the pressure). A coupl;e of potential systems I've looked at include system stores such as the Glow-worm Ultrapower 170SXI , Ideal Istor HE325 or Potterton Powermax HE150. My other main option appears to be a regular boiler + megaflo or similar. Any thoughts/advice on which way to go ?