I'm in no position to dictate what to do... but

))...
Maybe hold off buying an overdrive pedal until you get a GK.
I love GK... I play about the same genre as you I think, given the sound you're after in the YT link.
Those Backlines can get really scooped and gritty. Even better than my GK 1001RB-II. Which also can growl but I admire my GK for it's clean headroom.
I am waiting until the GK MB Fusion is available.
The BDDI is great, but it's going to be redundant (and a waste of money) if you are planning to get an amp that is going to deliver an overdrive sound that is in the ballpark.
The BDDI is an awesome pedal though. But save your money for a GK.

Again, my opinion, its not up to make to make decision for you.
For further reading, search in the amp forum for a thread: "the much talked about Gallien Krueger growl"
edit: link to thread:
http://www.talkbass.com/forum/showthread.php?t=587141
Makes for some good reading and experiences from GK fans if you have some time to kill.