James & Skub, thanks very much for your ears and opinions. If it was a real piano I'd love to feature the pedal sounds and stool creaking, but for now I'm confined to imitation pianos, albeit this one being quite realistic in my opinion. Maybe adding a touch of room noise might add a certain something though. As for reverb, I deliberately wanted to keep it light for a more up close & personal feel.
You're probably right about boominess - I haven't got a great room or great speakers, and the speakers I do have are ones I'm not really used to yet. I'm not big on headphones, although I did use them for a very quick reference listen-through, I always use speakers for mixing, because that's how I hope people will listen. Maybe I should reconsider that...
Thanks again chaps. Onwards to mixes 6, 7 & 8!