I love the K1000 and use my own a lot. I also enjoy working with the KX as they are very similar with the exception of a few additional features. On the surface it would certainly seem that a KX should be a better deal than a K1000. But I would have to say that would only be true if the KX were at least in as good a shape as the K1000.

The shutter in the KX and K1000 is the same, and should sound fairly much the same. They are both cloth, horizontally traveling, focal plane shutters. Neither camera ise very quiet but I cannot tell any real difference between the shutter sounds in either my KX or my K1000. Any differences in sounds would likely be more related to the current condition than to differences in shutter construction so it would be an indication to me that the mechanical condition of each camera is different. If possible I think it would be a good idea to have the cameras checked before you make any decision. At a minimum, take off the lens, open the back of each camera, and fire each camera's shutter while watching from both sides. I suspect the sound you hear is actually the mirror swinging out of the way and dropping back down. The noisier of the two may have bad mirror bumpers. But a lot of times watching the shutter and mirror work can tell you a lot. Or, take them to a camera repair person.

Either way, both are very good, very reliable cameras, so you can hardly go wrong with either.