Oil Temps
Steve,
Unless you have a suspicion and have confirmed abnormal oil temps, (those approaching near 300 deg.) then no I don't see the benefit for a CS.
Properly engineered oil coolers usually have a built in t-stat/ bypass, so low temps shouldn't be a problem.
Don't know what you're considering, but used is something to be cautioned about. Just like radiators, they tend to catch everything, and unless untrasonically cleaned and checked for cracks; it's not a good idea.
From a practical view- it's something else to leak.