Would you help to dress me for my new office job? - Page 2
Also, jackets/sportcoats are out of the question from what I can tell. Maybe in the winter or with client meetings.
The problem with your dress code is that it is disharmonious. Any outfit without a tailored jacket is casual, but a tie is more formal. I would never wear a tie without a jacket. But I agree with others that you should not try to get the dress code changed to require odd jackets to be worn.
Within the parameters of your dress code, the advantage of the silk knit tie is that it is a casual tie. Therefore, it helps attenuate the tension in the dress code and shows a certain amount of insouciance. But you need to work out whether that is the right message to send (although I doubt how many people in the 'real world' really notice or care about these things).
If you think a silk knit is a bit too much, but like plain ties, then try to find some with some texture. Avoid a shiny satin. You could try repp, wool (in the winter) or grenadine. For some examples of the styles, check out www.samhober.com.
EDIT: Oh, and with colours, it is hard to go wrong with navy (as has been suggested) and dark red / wine. I personally like bottle green but not all would agree.