Awesome subs. I personally have the xfl 15's and we burped them on 2 saz2000's at .5 and they were still asking for more. The owner of the shop I work at had 2 of the xfl 12's on 4k daily and they took it just fine. Now my other friend has 2 of the xfl 12's on 4k daily as well and he might upgrade power for them. Very strong subs. Also the comparison of them to the sa's. Sa has 2.5" coil, xfl has a 3" coil. Xfl's with the new basket design have A LOT of cooling. Plus they are rated higher. My over all opinion is great subs and built very well. If you have any more questions feel free to pm me.