The Yams were indeed excellent - the clarity with one of my Platipus tracks was breathtaking... I felt like I was able to 'see' the whole of the arrangement in space. They were let down a bit by some of the 'larger' tracks though, and I did feel that the bottom end lacked something, but I was half expecting this following the info posted here.
Next up was the Alesis. I heard the 'booming' guys here had mentioned straight away, but if required, I knew that this could be tamed. The clarity in the mid range didn't seem as good as the Yams, but I really enjoyed the overall presentation of my sample tracks, from top to bottom, and I ended up getting these.
Although the spacial separation didn't appear as clear to me at first as the Yams, I did start to see it happening and I'm going to enjoy using the Alesis and learning all about them.