What size is going to show me the wonders?

As being fairly new to this hobby, I have been observing with an 6" chineese refractor. The planets look great , but those faint fuzzies are just ,well , faint. I'm thinking about going newtonian , most likely a dob, and was wondering what size would you guys suggest as a minumum apperature for resolving most of the heavenly wonders ? To keep things simple , I will probably downsize my refractor so I can have a grab and go second scope.I live in Chicago , so I need to drive to a darker site. Weight / size is not an issue.

I like 8" f/6 because it is big enough to show a fair bit, and small enough to get used a lot. However, if you really want to see more 14" f/5 is supposed to be another good point for usability versus light gathering power. I have had some experience with a 16" f/6 (not my own). It certainly shows a sky littered with NCG's, but it's hard enough to use that It rarely gets out. At f/4.5 or even 5 it would be better, but also more specialized.

My personal ambition alternates between a 14.5" f/5 and a 12.5" f/6.

My vote is for a 12.5" f5. Plenty of light grasp, not too much weight, yet you're still able to observe with your feet on the ground.

I have three reflectors, an 8" F/6, a Starmaster "shorty" 11" F/4.3 truss dob, and a 16" F/4.5 truss dob. All have excellent optics. If I had to choose one, I would go with the 11" Starmaster. It has great Zambuto optics, sets up quickly, and can be used seated at all times. The Shorty gives better planetary views than any scope I've ever owned, and 11" of aperture is enough to pull in most dso's.
Rob Mackie