Adam,
In regards to your inquiry, I'd have to say that Artisan is the best choice for smoothing out the curves you already have. There's a bit of a learning curve, and a small price tag, but the results could be stunning. In the future, you can adjust the amount of segments SU uses to draw curves in the user interface. When you first hit the circle or arc command, look at the box at the bottom of the screen and it should tell you how many segments you are drawing with, you can increase or decrease them to suit.
I've been away from Podium for too long to offer much advice with the renders, and many here have better opinions on what to use for a rendering software. I personally use Twilight because the price is right for the amount of options you get, but I'm seriously looking at Thea these days...
Cheers!