Dell is useless. Their response is "don't upgrade the cpu -- we don't recommend that" (even thought they offer the studio 540 with that chip). The q9400 will work. The entire problem is that to enable virtualization you need to enable it in the BIOS and Dell has told me "we don't support that". They are unable to tell me whether or not the feature would be enabled with a new chip.
There was a recent "critical" bios upgrade posted for my machine dated 12/15/09 for version 1.0.7. However, my machine currently has version 1.0.12 dated 5/xx/09. A new post with an earlier version number? And Dell can't tell me why or even if I should upgrade.
Dell customer support is useless.