component order on a rack?

Turntable on top, next is the preamp cuz ya fiddle with it quite often (and you don't want to get on all fours to adjust the gain or change input selection), next is the CD player (for the same reasons as the preamp), then tuner, and finally the amp on the bottom shelf.

Your order makes good sense. The only other caveat I would add is that you may require a fairly long phono cable that passes potentially RF-noisy components. When I did this, I cut the noise with a pair of Audioquest RF Noise Stoppers (sold by Audio Advisor and others). They worked well.

I place the CD player directly below the TT (which is on the top shelf). The reason being that it is easier then to place software in/on either and this reduces the risk of damaging precious CD/LP's. The preamp controls require less finesse and the 3rd (from the top) shelf is not a problem. I also have to relevel the "source" shelves from time to time (as the building settles) and having them towards the top makes this an easier task. My tube power amp is currently on the bottom shelf, but I plan on relocating it to a separate wall shelf (above the equipment rack) in order to reduce ambient heat effecting the other components. Off to the side would work as well, but this is not practical in my setup.

another caveat re: component placement: if you are using a separate phono stage or a
preamp with a built-in phono stage, it should be placed in close proximity to the source
and as far away from the amp as possible. in my experience, it is ALWAYS better to place
your amp(s) as close to your speakers as you can get them and as far away from your
source(s) and preamp as your environment and budget for wire permits. -cfb