2 years ago (and I think it was the same this past year), iSci used the same books as other first year science courses.
This means that there will be tons of used books, and if you wait until September Titles will not have already run out.
I don't think anyone on the forum is going to want to guarantee that the same books will be used next year - what if one of the profs does some research over the summer, and figures out that there is a better book available?
Also, keep in mind that if the books stay the same, there will be lots of 2014s (and maybe some 2013s) who will want to sell their books for a lower price than Titles. So at this point, waiting is your best option.
Congrats on your acceptance!!!