Howdy TUCQUALA,
I'm a fan of series unless limited by your controller.
I'm not familiar with your charge controller so had to look it up. It appears that it will take a maximum input voltage of 48 volts. Based on that, I would go series. However; confirm that the unit you have in hand matches what I found.
Edit: Sorry, didn't answer all your questions. You can add a second 150 watt panel. If connected in series, you would see a maximum of 22.5 volts and 16.76 (8.38 amps times two). If connected in parallel, you would see a maximum of 45 volts (22.5 volts times two) and 8.38 amps. According to the specs I see for your controller, both are within it's limits. Also remember, panel "max" specs are under ideal conditions which don't exist in the real world.