And me! You're quite right. The MoCo has occasionally sold bikes with decent suspension, such as my 2003 FXDXT, which had fully adjustable suspension front and rear, as does my Firebolt, but I don't know of any of the touring range being so fitted. At the very least the CVO models should have the best suspension available, bar none.

 

I went with Progressive monotubes in the front and their 944 shocks in the rear. I went with the 1" lowered set up. I'm very happy with the ride now.

 

Judging by your SIG pic, you still may need to lower it a bit more. You can barely touch now!!!

 

The "best" fork springs are going to be the springs with the correct spring rate for your weight, regardless of what brand of spring you use.

And as others have pointed out, damping is an important component of suspension operation also. The Ohlins cartridges or something like that might be a good way to approach that.