What type of music do you play?
GK has always been pretty popular for double bass, but I don't see too many guys using the Goldline stuff. I have not tried one myself.
The rb series (400rb, 800rb, 700rb) of heads are very well liked by alot of rockabilly, blues and country players, and then the little MB150 combos are used by alot of Jazz players.
As for pickups, if you are using the original (clips on the bridge) Fishman, then just about any other pickup is going to be better.
Some popular pickups are: the Underwood, Revolution Solo II, K&K Bass Max, Fishman Full Circle, David Gage Realist (best for lower volume applications) , and the newer Planet Wing. There are many more.
Many players also use a preamp to get a better sound and allow for extended EQ capabilities and take advantage of feedback fighting features. The Fishman Pro Platinum Bass EQ/DI is a very popular one, and I use it myself.
It would probably help you get better help also if you fill out your profile, so folks can see what sort of music, bass, etc you are into.