Note there is no difference between preferred and regular economy seats other than the location in the cabin. The E+ seats do have more leg-space, same seat. There is no service difference.
Thanks. I am aware of that. What I'm hoping to do is select two of the three center seats. If the flight's not full, since there's a charge for it, I'm hoping the third seat won't get taken. That'll let the two of us lift the armrests and spread out over the three seats. On the other hand, if the flight does fill, I'd be game to shell out for the Economy Plus.