While the 3913 and CS9's are fine guns, they are not going to feel as good as your 39. The shorter grip and straight backstrap of the 3913 come nowhere near the comfort of the full size 39 series guns in my opinion. I carry a 3913 when I need something smaller, but much prefer the full size, single stacks. I would venture to say the curved backstrap of the 69 series, despite maybe a little more thickness, feel more like the 39 then the compact single stacks. I agree that a 439, or another 39 obviously, would be most like what you are looking for and pretty cheap if you aren't too concerned about condition. I have a 639 and love it, but it and the 539 are going to be heavier. Same goes for the 3906 plus it and the 3904 have the nasty square trigger guard. I wouldn't worry about the sights either. On the other hand if you get a gun with the fixed Novak sights there are plenty of options to replace those with adjustable sights if they don't end up suiting your fancy.