Going to purchase an amp soon and during research I have looked at ATI amps. ATI says " The amplifiers are modular; each channel resides on a separate,plug-in circuit board, so increasing the number of channels is easy. You can go from a five-channel AT1805 to a seven-channel AT1807 in a matter of minutes." Has anyone done this and if so did you have any problems adding more channels? Did you have to send the amp to ATI to have this done?