the STS is the rubber string stopper that mounts behind the stabilizer and is a good addition to any bow,IMO. the TRG/SOS is a total piece of crap. avoid it if at all possible. but dont let that keep you from buying an Exile(a.k.a. Cheetah). you can get a free replacement from Martin in the form of the traditional cable guard rod n slide and even strings. the Exile is a fun bow to shoot and is extremely accurate as long as you can get used to shooting a short bow. 30-32" ata is my preference and i shoot them better than longer bows. it all depends on the person. with its 30" ata it can be a pain to get used to as its not as forgiving as a longer ata bow would be. but it has good,speed,smooth draw,quiet and accurate. not for shooting with fingers. a release is a must. hopefully your questions have been answered. welcome to the forum. post pics of your bow when you get it.
'07 HCA Iron Mace
'08 Martin Bengal
'11 Martin Exile
Hutch~N~Sons strings