[Somnium (Aidan)]

I don't think you will find a ccd that is good for both planetary and dso imaging, they have different needs. For planetary you need a small sensor that doesn't require a physical shutter so you can get a high frame rate , you need lots of short exposures. The camera doesn't need to be cooled and in fact there are cheap solutions such as a webcam (such as the toucam) that work quite well and are inexpensive. As far as CCDs go for dsos, there are a few things to consider

1) mono or colour - colour is a nice step up from the dslr you are using, it will give you temp regulation with a much less noisy image but the post processing will largely remain the same, mono on the other hand will give you 4x the resolution because you now have 1 pixel doing the lrgb work instead of rggb single pixels that make up 1 colour effective pixel. Mono will also allow you to image in narrowband so if you are keen to get those Hubble styled nebula shots you will need a mono.
2) what do you want to shoot? The wider the fov you want the bigger the sensor needs to be and the more expensive things get
3) how much do you want to spend
4) what kind of focusser do you have, it needs to be strong enough to take the weight you will be putting on.
5) the noise of the system , the read noise and the dark current. The higher the noise the more , and longer, subs you will need to get a good signal to noise ratio
6) pixel size , you might not want to over sample or under sample depending on what your goal is
7) this is a bit difficult to find on a web site but ideally you want a ccd with a noise pattern that is consistent so it can be removed in prepossessing
8) quantum efficiency, how efficient is your camera at turning photons into electrons, the higher the qe the better the signal to noise for any given sub
That is all I can think of right now but check out the blog post on the sbig site called choosing a ccd, it goes through most of the above in more detail.
The most popular of the CCDs is the 8300 chip which has a good overall spec and is reasonably priced , you may want to start investigating there. Once you choose the chip then you need to select the manufacturer ...