I tried several different scopes when I had my CFX. Started with a the BSA 2-7x32 AO it came with, not bad, but wanted more power and better light "gathering". Most of the time I had it I was using a Leapers 3-12x44 full size, with 30mm tube. Although large and heavy, this was an excellent scope for the CFX, very bright and clear, and a very good power range. I had it in an Accushot 1pc. medium mount. As good as the optics were, the mechanics didn't hold up, at least for me. In fact, of 6 different Leapers scopes I've had in the last year, all have had problems. Considering the number of people that swear by their Leapers scopes, I can only assume that a chunk of it is sheer rotten luck :-)! If you'd like more info on my Leapers saga, look under the Scope Reviews.
I had a Simmons 44 Mag for awhile, good scope but I never liked it as well as the Leapers and got rid of it. This is another scope that lots of people really loved, too bad Simmons discontinued it.
Like Gerry, I recently discovered the Nikko Stirling scopes. I don't have one of the Airkings (YET!), but I do have a Platinum Nighteater 3-10x42 on my HW 77. Exact same size as the one Gerry has, main difference I know for sure is that mine is a side focus parallax adjuster instead on the front objective lens. I think the lenses and coatings are a little more upscale, but that's a guess based on web site info. I haven't done a side by side comparison. I think either one would be an excellent choice for a CFX. BTW, I got mine from Cheaper than Dirt, $123 with shipping.
For the shooting I do, I feel that a 3 or 4-12x is about perfect, and a front objective in the 40-44 mm range also works well. This gives a nice balance between weight, length, and power, and still lets you mount the scope reasonably low if you prefer. And I think I've run on long enough :-), hope this is some help.
Dave