Bollocks to a new transformer being necessary. If the off the shelf kit transformer is 300W and delivering 12V at its secondary tap, then you can sucessufully deliver enough voltage to the fixtures in a simple system with the right wire and good connections. Its a matter of understanding and technique.
This guy is clearly looking for a simple solution to a simple system... lets not dismiss him becuase his technology and techniques are not Pro Grade.
Please contact me directly via email or phone and I will help you through this.
Have a great day.