which SET/Corporate Account # will provide me the lowest rates?
There is no answer to this. There are probably 10,000+ SET codes. Depending on the cities, time of the year, day of the week, size of the company, number of nights the company's travellers spend with Starwood each year, etc., etc.. etc., different SET codes will yield different prices. If you could find all SET codes (I suspect that they are confidential), it would still take more time than it is worth to try to determine which really is the lowest for a particular stay/place.
Welcome to FT. There is a Search button at the top of the forum that will enable you to search on all of the threads regarding SET #s. Enter the keyword SET and you will receive several threads; one was just discussed last week. If there is anything else you may need, please feel free to PM (Private Message) the two moderators for this forum (located in the lower corner of the screen); we're here to assist you and hope you have a great experience on FlyerTalk.