A900 Should sound better out of the box anyway. I gave my A500 100 hrs to settled down. while after 70 hrs. it remains unchanged till 100.
A900LTD's are real candidate to burn-in properly. Now I have 36 hrs + 25 hrs previous owner. approx. 60 hrs. It's changing drastically and I am on honeymoon phase with it now. But still needs to be more perfect. coz some time during burn-in it disappoint me for a while. then come to it's performance again.