25hz is a bit on the low spectrum and this is coming from someone who loves the low notes.
It may just be the way my truck loads but with my box tuned to 28hz it peaks sealed at the dash @ 26hz.
It'll play music all the way to 23hz before it starts rolling off too bad.
It's even more nasty with the doors open which is a bonus for parking lot demos.
I'd say 27hz is the lowest I'd tune any in car box.
Again, this is all just personal preference and you may do as you please, just throwin' in my two cents worth.