bought: gk 1001rb II + gk neo 2x12

That sounds like a great rig. Adding another GK neo 2x12 would certainly give your sound an added boost. Whether it's necessary for you, only you can decide. It depends on how loud you have to play. When playing outdoors, most bass players (and everyone else in the band) plays louder so may need the extra boost from adding another cabinet.

I'd certainly be very happy to play your rig if I needed one with that much capability. Enjoy it. Good purchase. I'm a big GK fan and have used them for many years.

 

nice buy man! post some pics?

 

Or, you could mix and match. Get a GK 1x15 or a 1x12 and add to the rig if needed.

 

I use the 1001rb-II with the Neo 2x12 and a Neo 1x15. Using 2 cabinets will let the head use all of its wattage and move more air. It gets really, really loud. Most of the time I just use one of the cabinets, but it's nice to have access to the extra power if its needed.

 

Too much boom huh? Well I have a 4x10 and a 1x15 and they sound brilliant with that amp. I'd say go to the store (the GC carries them all) and try out different combinations for yourself. I know it's not the same as an outdoor gig, but you never really know until you try it.

I also like the suggestion of a 1x12. That would really give you small gig/large gig flexibility.

 

It's all a matter of tone. I used to play through a 4x10, but lately I find I prefer the sound of the 1x15. The 2x12 is nice as well, but I tend to go for the 15 if I'm only using 1 cabinet. You really need to listen to the different cabinets and pick the ones that sound best to you. Certainly nothing wrong with 2 2x12s, but hear for yourself.

Also, the amp is only going to put out 750 watts total regardless of which two cabinets you attach to it.

 

You can add a 2x10 to give your sound more definition..