If your 105 groupset has a compact crank 50/34 then you can't really do much about a smaller chainring without replacing the whole crank, which could be done by using a subcompact, 46/30 but it won't be cheap. Not sure what cassette you have but you likely could get an 11-34 to work though you might have to change your rear derailleur as well if you don't presently have the 105 Medium (longer) cage. Bottom line is..... yes, you can get a lower low but how much do you want to spend and how low do you want ?