> It's velar. Same sound as a k, only it's a fricative, not a stop. That is, air keeps flowing. Move the back of your tongue back up to where you'd have it for a k, and blow. It helps to have spit in your mouth for this. That's your German 'ch', or as I like to call it, [x]. But that's getting a little technical there... ^^
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Actually, there are two pronounciations of the ch, depending on whether it follows a "dark" (o,a,u) or a "bright" (e,i,ä,ö,ü) vowel. There's a problem with your explanation: I don't know exactly where the ks in English are pronounced, but if it's anything like German, there are two different ones selected intuitively: a palatal and a velar. Interestingly, the other ch (called the [ç], I think), the one that follows bright vowels, is palatal.

> Oh, uvular r... How I hate you, uvular r...
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I could say the same about the alveolar trilled r. I am completely unable to pronounce anything *but* the uvular trilled r (or, sometimes, an untrilled rascalization thereof that results in a [x]) or the soft English r.

Fuzzpilz