If you are talking about a 2006+ XXX then yes they require a much bigger box. However, if you can find a 2005 XXX you are in business, that sub in that box will sound f'ing *******.
Keep in mind that the BP1200's will do north of 1400 at 1 ohm, and roughly 1300 at 2. I had a 15L7 dual 4 on that exact amp and it pounded the piss out of my car.
I think the problem is that your port is only 4.25" away from the back wall. I don't think thats good when your port is 8.25" wide. You're choking the port off.
rickiesdiscountelectronics had em for cheap but i just checked and they are sold out. You could easily get em for under 300 shipped if he had any. I bought 2 15" SE D4's from him for 298 shipped a few months ago.
A good question to ask is why did that resistor fry in the first place? If that resistor fried theres obviously a reason behind it (something shorted). You could put a new resistor in there only to find that the new one dies in a short period of time too. You could try a new resistor if...