Great stats Undergarun.
Could you please give us the average amount of players ?
Well, I will perhaps test read/write isolation with a clustered MySQL on low populated server, but I'm still afraid of the database consistency due to the replication. For your information Tungsten cluster does replication very easily, and it includes a connector with SQL read/write splitting. On two VM (single core 1,6GHz with 512Ram) I got some nice perfs (around 700 rw/s). PM me if you need some information on how set it up.