Boy I really don't know. I'd think they would be ok together, but betta's can be tricky. Maybe you could try it and see? If the betta won't let him alone, then you'll have to return someone... If there are some floating plants that might be helpful to seperate their territories a bit...
You and me both, Bettagurl. :/ I saw a Ram at Walmart (of all places), and hubby and I were both like... Wow. But I'm hearing that 15g is often the best for them, so I'll probably end up with a dwarf gourami.
I'd go with the ram over a gourami, especially with a betta. The gourami will hang out at the top of the tank, so will the betta. The ram on the other hand will hang out at the bottom. The cave and water sprite sound great.