Output Transformer

Here is the Output Transformer for the Valve (or Tube if your American) amplifier that I am building. I had a chap around the other day that is a serious Audiophile and he was more that somewhat worried about my choice of transformer as these are actually quite cheap at around $25. For a proper Single Ended amplifier I should be looking at something like the these transformers, which are over 10 times the price. I am sure that they are better but I seriously suspect that the laws of diminishing returns kicks in... The mouse looks particularly grubby dosen't it?