I really like the SW112/115 combination and expect you'll be surprised (and pleased) at what that 112 adds. On the flip side, don't freak out if you compare the 112 alone beside the 115 alone using the same amp settings. That 112 will not be as deep or as loud on its own as the 115, but can really deliver more than you might expect with a little extra EQ and a bit more power behind it.
I was shocked at how that 112 would come alive by itself with just a few minor adjustments. The 115 is just so big and present by itself, it's not a fair comparison if you don't give the 112 more to work with from the head. I played the 115 first and until I recognized this, I felt a little let down by the 112...not anymore!

Enjoy!!