Beate,
If you're happy with the paper prints you yourself get done, then you're good to go! I don't worry about softproofing any of my prints, since I know the printer in N.C. is a professional lab and will get them close and that's all you can ask. One of the issues that is rarely brought up, is the other end of the Internet, the buyers monitors,which I can guarantee you, aren't calibrated. so what they "see" can be close or off,based on their monitor's accuracy.
If you were doing a large run of a specific image, then I would bother to get a soft proof made or send one of your's to your printer and tell them to match it,
Rich