If you're going to do the lighting, I'd highly recommend getting your transformer from VOLT. Their transformers are built like bricks. They've got nice stainless steel cases and a lot of features too. If you go LED, you can run a ton of stuff off even their smallest ones. I've got 2 of their transformers. One big one in front that runs all my landscape and path lighting out front, and another small one that runs the deck and the back yard up lighting. I got the Trex post lights on clearance from one of the online sites. It was "last year's model connector," so they were like 50% off...I didn't care as I was just going to cut the connector off and solder anyway. Stair lighting is almost a must. I almost didn't do the lights on the posts at the bottom of the stairs, but I'm really glad I did.
The spacing looked bad to me at first, when my last frame of reference was wood, but I don't even notice it now. It's also nice because snow and water, and even small debris clear a lot more easily.
Dumb question, but do these transformers just plug into your normal outdoor outlet on your house?