When I bought the car, it would completely die out when driving, the ABS light would come on the dash then I would completely loose power. This sounded like a classic alternator issue the previous owner had had it replaced several times before I purchased it. So, I was very skeptical on that being the issue and sure enough I had the alternator tested and it was fine. There were aftermarket subs installed on the car, so I disconnected those this seemed to resolve my issue for about a week but driving to work one night it died out on me again I believe it was because I had mostly driven it during the day and was not using headlights. When jumping the car off it cranks up with no issue. So, when getting off work I purchased a new battery, and this seemed to fix the issue for about 3 weeks. But yesterday after driving for about 40 mins and stopping somewhere when I cranked the car back up it was not turning over well like the battery had low amps. Then when I made it home and parked it, I was unable to crank it up in the morning for work. I'm wondering where I should even begin to address this issue any help would be greatly appreciated!

What is the battery voltage before start attempt?, what is the battery voltage after start?; your connections are solid? (battery + to starter, ground, post are not corroded...)