Madalyn,
I ended up getting exactly what I wanted: A double row potato plow. It performed exactly as I imagined it would, too.
I ended up not using it as much, however, because our soil is extremely sandy. The sandy soil means that the perfectly formed raised beds were draining off the water way too quickly, and my plants suffered tremendously.
I also have a double bottom plow, and I used that to make a bed for my blackberries. The bed was about 6' wide which was just about perfect. That's how I'll be making any beds that I do make from now on.