I've only used unpowerered before.
What are the perils of using those - could that account for some of my "uptime" issues after adding another card (and on a riser) in - what I hoped was an easier to cool rig

What about over powering your PSU - i know you can use 2 psu. But do you join the grounds of at least one of molex pins from each psu - or doesn't the variance in "true ground" bother things?