I just repositioned my dish and got a "jumping" quality signal. Before that I was receiving
G25 (97W) at about 35-40 on my Viewsat Ultra, and 45-50 on my Pansat 3500. It turns out that I was pointing to about 96W and getting interference from G3C. When I moved the dish slightly to the west I received a good signal from G25 (good meaning the same as I noted above). I'm not sure what level the CW 600s will show, but it should be approximately the same as my two boxes. I have a similar size antenna as you and I'm in Toronto, Canada.
Oh, BTW, try blind scanning when you get 60% quality. If you get a channel called AON that means you're pointing to G3C (95W). As I recall, it happened to me when I was trying to get G25 a while back.