Played both SoC and CS. I never have finished CS because SoC is just so bloody amazing with mods. Steve, once you get the true ending (it is worth it for the final battle with the Monolith) head over to this site:
GSC Game World - Official Site and then go to the Mod Downloads section in SoC. The two mods I recommend you try are the Supermod Pack Version 2.4 as this also makes the game never end and you can flick back between levels and basically do whatever the hell you want, plus it lets you join any faction, drive vehicles, fixes bugs, adds a whole bunch of new artifacts, the list is endless. Then try the Priboi Story Mod. That is the one I am currently using and it changes the whole game as you now play from the military perspective. Been using this mod for weeks now and still not completed it.
Need any help, just ask, this is easily the best game I have ever played and is the only game I have played for weeks