I was reading up on trying to build a diy sub. I was looking for a low budget option and came across the infinity 1260. The only box I was able to find was one with a slot port. What I was wondering is there any way to build this with round ports? I'm not sure how to use the calculators so any help on this would be greatly appreciated. It will be used for home theater, and tuned as low as possible with the 300 watt bash plate amp. I think I've got everything in there.