Cool, I wondered if anyone had done this with a 5.
The church band does a lot of stuff in Bb and I've been going crazy not having a low Bb. My B string is a .135, so I think it would work at A.
I just might give this a try!
You should really find a 15" sub to pair the 4x10" to satisfy all your needs, that's what I do:
Ampeg Svt7 (1,000w 4ohm) thru
Ibanez Promethean 4x10" (1,000w 8ohm) and
Ibanez Promethean 1x15" (300w 8ohm)
Not all 15" work fine tho'... I encountered some problems with Hartke, both XL series and Xdrive series, for instance
or look for an Eden 4x10" 1,000w 4ohm (more expensive...)
Cheers,
Wallace