Hi, I bought a 6" Meade LXD55 Refractor this summer, so I am still fairly new to astronomy, but the single best piece of advice that I can give you is to try not to have too high of expectations for what you will really see. I fell into that trap at first, and I expected to see Saturn, etc. like you see them in Sky & Telescope, Astronomy magazine, and so on. Those nice, big, colorful pictures in those magazines, however, are either hubble pictures or pictures amateur astronomers have submitted that they took using either expensive CCD cameras or digital cameras. What you will actually see through your telescope won't be nearly as dramatic as those pictures. Now I'm not trying to discourage you, and this also does not mean that you can't see some neat stuff through a telescope, because you can.
The key, really, for planetary viewing is waiting for the moments when Earth's atmosphere becomes calm, and then you can definitely see some nice surface details. The viewing conditions are different from night to night, so some nights the atmosphere is very unstable and you might not get those precious moments of clarity that you need. Planetary details, while definitely visible, don't quite jump out at you, so you kind of have to train your eyes to see them.
I've looked at Mars recently through my 6" refractor, and I was able to detect some of the dark surface areas like Syrtis Major, and I could also see the Northern ice cap, which appears on the south end of Mars due to the inverted image. The ice cap on Mars appeared to be a bright dot in my 6", and Syrtis Major was fairly subtle, but you could see it. The last night I was out, Syrtis Major kind of faded in and out a little as the atmosphere's stability fluctuated, but there were moments when I definitely could see it clearly.
I haven't gotten a chance to look at Jupiter or Saturn yet, but I've read many posts saying that they've seen the Cassini Division in Saturn's rings, and it sounds like the main cloud belts on Jupiter are routinely visible. But to see the great red spot, and more intricate details within the cloud belts will require a night with a stable atmosphere.
Aperture (the width of your telescope's mirror) is a huge key to what you can see, and with a 16" aperture, you have plenty of aperture, and you should be able to see more detail with your 16" dob than I can see with my 6" refractor. Your dob will be fantastic for looking at deep sky stuff like galaxies, nebulae, etc., but I have only done planetary viewing so far, so I can't offer any advice or info about deep sky objects quite yet. Aperture is king for DSO's..
If you want to look at planets, I would start with Mars, it is still a great target, and is high in the Southern sky by 9:00-10:00 p.m. here in Iowa. I wouldn't wait long though, as Mars is getting farther and farther away quickly, so snatch a peak while it's still close.:-> It will be another couple years before Mars gets relatively close to Earth again.
If you are an early bird, I believe Jupiter and Saturn can be viewed just before dawn, and they are always nice targets. Mars, Jupiter, and Saturn should all be easy to spot with the naked eye, they should look like really bright stars and will stand out in a crowd. You'll know when you see them..
And hey, don't forget the moon! I never get tired of looking at all of the craters, etc..
So don't despair, there is still plenty to see.:) I don't regret for a second shelling out the $900 for my AR-6", it's been worth every penny. Believe me, it's really a gratifying feeling to see surface details on Mars and to know that you're looking at these details on something that's about 40,000,000 miles away. There are almost an endless amount of worthwhile objects that you should be able to see with your 16" dob, I doubt you would ever get bored with that scope..
One more thing, I think your 9mm eyepiece should give you around 200x magnification, which isn't a bad number, but there are nights some nights where you might be able to go 300x, which a 6mm eyepiece would give you, so a 6mm might be a good addition to your eyepiece collection. Another good option might be a good barlow lens. If you don't know what a barlow lens is, basically it multiplies your magnification. There are 2.5x and 5x Barlows. The Televue Powermates are somewhat pricey, but worth the money. I've been given one piece of advice about Barlows.. Don't by a cheap barlow! It sounds like a cheap barlow is almost more harm than good..
If you want more expert advice, I would pay particularly close attention to what danieldgj has to say, he posts on here alot and he gave me lots of great advice and information when I was trying to choose a first scope, learning what I can and can't see, etc. He's very knowledgable and you can trust what he has to say.
Well, I hope this information helped you, and best of luck.