just a question... have you played your Bass through a bunch of the rigs that they have at your GC? (I just notced that others have suggested this)
Take your Bass to try out amps.
Take your amp setup to try out Basses.
They will allow you to do that (if they don't .... walk.... your Bass ISN'T like any of the Basses on the wall, It's yours, with your strings and your goo.
(the stuff you put into your Bass over time, your fingers sweat & grime on the strings... your heartbeat and soul into the woods, what the strings vibrations (when you play) do to the neck, etc.) (sounds like magic, and maybe it is....)
I was just in my GC for the 1st time and they had a wide variety of Bass rigs.. with a bunch of different cabs.... take a day, hang out, play through a bunch of different stuff (and if someone comes in who plays well, let them have a go with your Bass so you can see what it sounds like when you don't play it).
As far as strings go, there are just a couple of formulations (well.... maybe more than just a couple) but start there.... do you like the sound of nickel?, stainless steel, flat wound? at least you can narrow your search down to a specific type... that's a lot less daunting than "the whole wall of strings" .
(I like Nickel, D'Addrio XL170s to be exact, I like the overtone balance, they are bright but when I play them on my Basses they never sound ... um... like John Entwhistle bright, just clear and full)
Best of luck
p.s. a 2X10 Avatar cab has some kick ass lows, or at least the ones I've played through did........
A SUB String Ray sounds great (but great like a String Ray, as mentioned)
And I can't say anything about your Amp, cause I've never played through one. I hope you don't mind.....