If it is a cable that you went to great lengths to match to your system then I'd recommend that you let the company do it. Both for the reason mentioned by Elizabeth as well as the fact that you will get a matching RCA, solder and terminating technique of the original cable, all of which can effect the sound of the cable.
If it is less critical cable it should be no problem, although some IC's use varnished wire strands so you will have to use a higher heat to burn off the varnish first so it will then accept the solder.
If it is less critical cable it should be no problem, although some IC's use varnished wire strands so you will have to use a higher heat to burn off the varnish first so it will then accept the solder.