Think of it this way: if you've never ridden a horse before, would you try to learn on a crazy bronco that people ride in rodeos, or a friendly pony from the county fair?  You could go for the bucking bronco, but you'll probably get hurt - at the least, you won't have fun your first couple times.

 

If you want to stick to those two brands, Burton makes lower-end boards like the Indie or Air, and GNU makes the Carbon High Beam, which is a great softer-flexing board.  All the good companies have boards meant for beginners, so you'll have no trouble finding them.  Ride makes the Cue and the Control, Rome has the Machine, etc.  You basically just want to stay away from stiff boards if you're new. 

 

Where are you going to be riding, and what type of terrain do you see yourself in (just groomers, powder, parks/rails)?  If you see yourself trying to learn park stuff and rails, you should go shorter, and if you're in the powder, go a little longer.  Regardless, since you're beginning, you should be leaning towards the shorter end of a 153-160 range, so 155 would be fine.

 

I'm almost exactly your stats, 8.5 shoe, 160 lbs.  I have a Burton UnInc (super aggresive, sort of like the Custom X) 156 and the GNU CHB 159. 

 

Personally, I don't think you can go wrong with the CHB, because it's soft and would be easy to learn on, but once you get a second board, you can always break it out for those mellow days where you just want to putz around and do butters down the trails.  There are tons of companies though, so just ask around.  Don't let anybody push you into buying a board just because it is cool or a pro rides it - make sure you get something that you can have fun on, rather than making your day miserable.

 

As far as boots go, Zags definately got it right.  TRY TRY TRY a the store.  Make sure they fit your foot well - different companies tend make boots differently, so not all size 9s are gonna be the same. 

 

... Can you tell it's a slow day at work?