The reason being last week I purchased a CA551p , I wasnt exactly blown away at first, the sound was not that dissimliar to the built in phono on my amp, but after a week its sounding quite delicous with certain tracks :roll: when I switched back to the internal phono, there was notibly more sibilance, not that the CA unit gets rid of it, but it 'seems' less obvious or have my ears just adjusted to a little differnt presentation, I have the option of retuning it this week or upgrading it by just paying the difference, Does the 651p sound better, apart from having the MC compatablity, The 551 does seem to have improved a little in the last day or so, I was goiing to return it, but I think its a keeper now !