Well I have much experience too with it all so..hmm I say dont go with the ccc's. But Robitussin Maximum Strength Cough. And depending on what plateau you want to reach would be how much you drink. Heres a Nifty calculater to determine by weight how much to take for desired plateau.
The Dextroverse - What is DXM?
I went with 8 oz bottle of it and its about 720 mgs and I was tripping balls. Ive never hallucinated off DXM..But also have never been in the 4th plateau. The only way ill gothere is with pure dxm. But yeah im babbaling. That site works =D. I would try 3rd before you get balls for the 4th haha..do the recomended does on 3rd plataue for your weight..which is 788mg 8.9ounces. So yeah instead of buying another just stick to 2 4 oz or an 8 oz. (same thing)