@rzamites
First, whatever you get, buy used. Pawn stores are a good source to keep an eye on. The best part of buying used is that you have the best chance of generally breaking even (+/-), if & when you decide to sell.
Next, find a comfortable to play Squier or MIM P-Bass and carefully remove the OEM pups and install your Geezer Butler pups. This will give you a bass that is at least somewhere in the same ballpark of what your custom made bass will be.
Then, take that bass and play it through various used offerings at pawn shops and or Craigslist/other ads, to find one that feels pleasing to you. The various suggestions of Fender Rumble offerings seem pretty spot on for a good starter rig. An Ampeg BA115 can also be pretty OK and often quite cheap. The B100R and B50R are fairly well regarded, for a little bit more.
Now, you've got a complete rig to practice up on and develop your skills to more accurately assess your custom built bass when you finally receive it, after swapping the P-Bass back to it's original pup. Of course, if you happen to decide that you enjoy that P-Bass enough to not want to part with it, another Geezer pup is only $120-ish!
Just My $.02 & Likely Worth Even Less?
Gene
First, whatever you get, buy used. Pawn stores are a good source to keep an eye on. The best part of buying used is that you have the best chance of generally breaking even (+/-), if & when you decide to sell.
Next, find a comfortable to play Squier or MIM P-Bass and carefully remove the OEM pups and install your Geezer Butler pups. This will give you a bass that is at least somewhere in the same ballpark of what your custom made bass will be.
Then, take that bass and play it through various used offerings at pawn shops and or Craigslist/other ads, to find one that feels pleasing to you. The various suggestions of Fender Rumble offerings seem pretty spot on for a good starter rig. An Ampeg BA115 can also be pretty OK and often quite cheap. The B100R and B50R are fairly well regarded, for a little bit more.
Now, you've got a complete rig to practice up on and develop your skills to more accurately assess your custom built bass when you finally receive it, after swapping the P-Bass back to it's original pup. Of course, if you happen to decide that you enjoy that P-Bass enough to not want to part with it, another Geezer pup is only $120-ish!
Just My $.02 & Likely Worth Even Less?
Gene