Box size reccomendations for Suburban

I have 3 12's and 2 18's in my suburban. Just running the 3 12's is enough bass with a big amp. I have mine running off a PPI PC2350. Hope this helps.

three 12's sound like it may be good. What brand 12's? What are the specs on the amp. I cant find that part number on PPI's site.

I have all JL audio w6's. As far as the amp, it is from the 1998 line and it is 350x2 at 4ohms, 700x2 at 2 ohms. It puts a lot more than that since it is way under rated. I have that amp running my 18's and then I have the PC1400 running my 12's. It is a mono amp that pumps out 400x1 at 4 ohms and 800x1 at 2 ohms. I have it going at 1.5 ohms so it is pushing quite a bit. You can get a lot of sound in a suburban and not have to use a lot of subs. I only did the 5 subs total for fun, has not practical use. May change everything up and get rid of the 18's, who knows. Hope this helps and good luck.