I voted the premise is flawed

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My first bit of advice is get some good ear plugs and accept what it means to wear them. They will degrade the sound, but IMHO it's worth protecting your hearing.
As far as battling with guitars. Your premise is wrong because this is a war that no one really wins. If you simply resort to sheer volume, IMHO everyone loses, including potential patrons.
A big part of the problem is everyone wants to hear themselves about 6-10dB louder than everyone else. Unfortunately there is not enough distance or isolation between players on the typical bandstand for everyone to get the desired 6-10dB, so volume wars erupt. One players turns up enough to get the desired 6-10dB and suddenly no one else can here. So someone else turns up to get their 6-10dB, and then the original guy can't hear, so a cycle of reciprocal volume tweaking ensues.
Keep in mind the low frequencies are pretty much omni directional so really cranking the bass tends to get on everyones' nerves. The frequencies of guitar tend to be fairly directional, but many guitar players prefer open back cabs, which are designed to spread the sound around.
Rather than trying to compete with the guitars, I suggest focusing on setting up and adjusting your rig so you can hear better without having to turn it up so much. The ear plugs are going to cut some of the highs you hear, so in order for your bass to sound natural you will need to roll on some high frequencies in your sound. If you leave you cab on the ground and stand close to it, the upper mids and highs are just going to shoot out in front of the cab below ear level. So in order to hear those frequencies, you need to get some of you speakers up in the air and aim them at your ears.
If you set up your rig so you can hear it easier, you don't have to be as loud. If you're not as loud, it won't cause the guitar players to turn up even more, so IMHO it's win, win

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The most powerful amp I own is a SVT8-Pro that is rated for 2,500W at 2 ohms. With the right speakers I could probably pummel a few guitar players into submission, but I would be abusing myself as well. Better to use an approach that allows me to hear without resorting to dropping a bomb

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Anyway this is how I approach the problem. It doesn't work for everyone due to philosophical differences, so good luck

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