I have a Bag End sub that can go that low - has two 10" speakers (similar surface area as one 15") - I have used with Tyros for larger gigs, it does add an impressive "feel" to the sound. I might use it with Genos for a larger gig I have early next month. For mains, (for these larger gigs), I use two FBT Maxx40a's which also are amazing. [For most gigs though, I use a Lucas Nano 600 which does real well).
If I remember, I can write about use of the true sub (Bag End) with Genos once I give it a try ...
Jim