Hi leftside, and welcome to The Mattress Underground 
Glad to have you here.
Sorry to hear your new Silk & Snow Hybrid is not quite as firm as you would like. Any mattress, regardless of type, materials, firmness and composition, is unique to the sleepers using it. Other consumers looking for a firm mattress might find the S&S too firm. Finding the perfect mattress is a matter of your Stats(height, BMI, sleeping position(s) and any underlying health issues) and your PPP(Posture and alignment, Pressure relief, and Personal preferences).
You might want to take a look at ourMattress Shopping Tutorial, as well as the Mattress Specifications You need To Know and finally the Mattress Durability Guidelines to get a better idea of what to look for, what to avoid, and how long you can expect specific materials to last.
Thanks for giving a couple of your stats; without your total stats, the Silk & Snow hybrid raises no red flags; if you are over your BMI and sleeping positions would not present any issues – you can see a recent discussion about the Silk & Snow Hybridin this post. The best way to find a mattress firm enough for you is, of course, trying out in person.
If this isn’t possible in your area, and/or you are considering purchasing online, many of the Trusted Members of the site carry Similar hybrid mattresses, and have excellent customer response. If you explain your experience with the Silk & Snow, and provide a little information, they can match the ‘feel’ of the S&S with slightly firmer foam components to more closely match what you are looking for.
Hope this helps,
Basilio