If you're not going to use ntrboot to restore a NAND backup or perform a CTRNAND transfer, then yes, a hardmod should be your only other option. You can use a hardmod to restore a NAND backup. If you don't have a NAND backup, you can use a hardmod to install B9S and then perform a CTRNAND transfer.
Think that's a softbrick. A hardbrick is when hardware is damaged/faulty. Or maybe I've been using the term wrong this entire time. Anyway...
ntrboot is what you want, I would not advise you to hardmod when there is a much simpler solution. ntrboot can unbrick any type of brick a hardmod can and then some. Plus it can be used on multiple 3DSes if you ever needed to.
@The Real Jdbye, no you got your terms right. hardbrick = hard(ware) brick.
Blue screens of death brick can be caused by either hardbrick or softbrick. It depends whether you corrupted the firmware image flashed on the NAND chip or physical damaged the NAND chip itself.
See my signature for link to the cheapest (but shitty) US $5 R4iSDHC series ntrboot flashcart. Reflashing that cart to ntrboot mode requires another (o/n)(2/3)DS(i)(XL/LL)(phat/lite) system. After installing boot9strap to the o3DSXL with SafeB9SInstaller, your o3DSXL may still experience blue screens of death if something other than the FIRM0/1 partitions that are corrupted.
You will need to ntrboot chainload launch GodMode9 as sdmc:/boot.firm for advanced troubleshooting (take a peek look in the [S:] SYSNAND VIRTUAL to see what items are missing).