[quote name='LukeFRC' timestamp='1426271610' post='2716496']
I had a GK 1001rb for a short while... if the amp is anything like it... turn the master output volume up near full and use the gain to control the volume and see what that sounds like.
[/quote]
I have a Fusion 550 and 1001RB and 400RB heads.
A GLX 410, RBH 210, Neo 212.
The Fusion and 1001 are quite different.
The GLX 410 is naturally warm. The RBH210 very punchy. The Neo is fairly neutral in comparison.
On the Fusion switch off the bright control, switch on the deep control. Back off on the gain, up on master. Even though your bass is passive, try the active position and turn up master. Play around with contour.
FWIW if I gig with only one cab tehn it's the Neo. It's the most versatile of the three for me. Use the channel switch (footswitch) to give alternative sounds.