30C at idle is good, so that HSF is doing what it should be doing... keeping your cpu COOL. How high your load temps are is another matter; if they're going above 50C at stock speed/voltage, not too good. (I won't lie to you, I don't know the stock speeds or voltages of the D805, nor do I have the time to research them right now... google away, you'll find your answers.)
You should keep your voltage as low as possible while maintaining a stable system. Adding voltage creates more heat, so only up the voltage if you plan to increase cpu speed.
What I do to stress my cpu and make sure its g2g (good to go):
1) SuperPi
2) CPU Burn-in (with dual-core cpus run two seperate instances simultaneously. This will provide %100 cpu utilization, use 'max heat generation' setting.)
3) 3DMark05 and then 3DMark06 (good for stressing both cpu(s) and gpu(s), if your pc has a problem this is the first stressor that will catch it.)
4) Prime95- with dual-core cpus set the 'affinity' to 0 for the first instance, and 1 for the second instance; you'll be running two Prime95's at once, and this will completely stress and heat your pc, more heat than CPU Burn-in. If you overclock and this fails, back your speed down until you can run this for at least a couple hours, I try for 6+ hours, most people don't call a system stable if it can't run for 24 hours.
Have fun...
TJS