[SimpleNatureSpirit]

I definitely suggest you upgrade to 6.4 or downgrade to v5. Early 6.x versions has some serious bugs, like loosing your takes, sessions not opening, etc. After all, the upgrade is free. Don't count on any gain improvements, however. That just hasn't been an issue. If you have a clean preamp, you might want to just switch MBox to line~in. With gain up that high, MBox is just not that clean.