Chances of getting sepsis from symptomless utis in people who are asplenic (those without a spleen)? is that rare or something to be concerned about if asplenic?

Yes, complicated UTI (pyelonephritis, renal abscess, and sepsis) is more common in asplenia. As advised in reply to other question(s), any asplenic person should be in care of an infectious diseases specialist to advise on this sort of question, and to weigh in if high risk infections occur. But understand that the large majority of splenic persons never get serious infections as a result.