Originally Posted by carl h.
If you need to spend money, add a 2nd ampeg 15. It will get you a bit more of everything you like about the cab at all volume levels, and it can get much louder with 2.
Bag End does make excellent cabs though. It's been a really long time since I've played through the SVT-15E to do a proper comparison. My guess is the S15D will be louder as it's more efficient. It's smaller and lighter too. The SVT 15 may have a little more of an extended low end, but not by all that much.
An 800RB into a pair of S15D's was my main rig for a long time and it KILLED. Very portable, incredibly loud, and just awesome bass tone. GK's pair up really well with Bag End cabs.
When I owned the SVT 15E I remember liking it, but it was a long time ago.
As a standalone cab, I'd say the S15D is an upgrade. I can't say how it would pair up with your SVT 15. It might work really well and it might not.