I've recently bought a big dob and find the range of useful eyepieces for different objects, much larger than for my 4" refractor. The only things I have against barlows is the fiddling around in the dark switching from EP to EP and the fact that they effectively halve your eye-relief.
Of course with multiple EP's, you're dealing with multiple $$$$$, but I'm leaning that way for the flexibility.
Try this site:
www.telescope-simulator.com
It gives a fair idea of what different FL eyepiece / telescope combinations will look like. Not 100% accurate, but close enough.
Good Luck,
Peter