The dress code has inspired so much entertaining exchange on the boards. I applaud the OP who has obviously read the information about formal and semi-formal night, and is seeking input on what is appropriate. She seems to be hoping that the less formal options are acceptable, but I sense she started the thread wanting to comply and not buck the suggested dress code.
Disclosure--I'm a tux guy when I get the chance, its fun and classy.
Dark Suits do outnumber tuxes, and thats just fine. Sport coat...hmm, my vote is for a nice blue blazer if not going to go w/ a suit, but I encourage a dark suit. But really, any respectable sportcoat and tie meets the spirit of formal night. I'm a little more formal again on semi formal night, as I do think a gentleman ought to wear a jacket of some kind on an evening dubbed semi-formal. But there will be many who do the tie w/o the jacket.
This thread seems to have given you a variety of responses but all from folks who are within a fair interpretation of the dress code.
And I'm glad there are others who understand that seriously casual in the sightlines ruins the ambience of a formal occasion, and part of the reason for a formal occasion is so that ambience will be a part of the total experience. oops, was on my soapbox for a minute there...