darul hikmah has almost the same scholars as darul qasim, but darul hikmah is more of a weekend learning for general folks. but its just adds to atmosphere of chicago from what I can see. Inshallah, may Allah make your path easy. amen.
In regards to the sahih sitta, I think right now darul Qasim is still fairly new. So I don't think as of right now they are teaching it, but once they get those students into the system and then get them to that level they will need to teach those books. but right now its just attracting the right students, getting them through their arabic program and into regular mode of study. Its not a big deal really, cuz either they'll be ready once you get there, or send you to another institute like iie, also in chicago, or teachers from there could potentially teach at darul Qasim in the future. Ideally you want to learn those books from someone who has been teaching them for decades, and those teachers are generally found in the madaris, and least in the dars-nizami system.
Im sure you're aware of the other madrasas, like buffalo, chatham cornwall. but I think for your age, Darul Qasim is prolly best, cuz they are trying to attract older serious students, as opposed to younger teenagers.
I was just looking at Darul Qasim's website again, in the about section, it says they have designed a 3-yr curriculum. So I guess there you have it. 3yrs won't include the Sittah. It also says they have 25 students, so clearly still growing. But I would not make a decision based on sittah. I'd make it based on family ease, your ease, and solid arabic studies. in the future after the fundamentals you can always to go the exact place that is best.