Just to qualify, I've been a bassist for 58 years and an audio engineer for 50 years, the last 35 of that as a mastering engineer. Whether that means anything or not, I have some insight on speakers you probably won't like. For what you're saying you want you don't need the thump thump. That's not where the bass lives, and too much of that will hurt the situation by murking up the mid bass and lower midrange where the meat of the bass guitar is. As far as articulation of the bass line there's not much below 60Hz. or so that will do you any good and will instead get in the way, especially if you boost low bass. The thump you're desiring is in the 40 - 50Hz range and that's where the meat of the kick drum is, not the bass. Even though the fundamental of the bass's low E is approx. 42Hz., what you really perceive is the 1st harmonic at 84Hz. On a five string the low B would be around 31 Hz., but again it's the first harmonic at 62Hz. that you really hear. So what you need is a good pair of studio-quality bookshelf speakers that have good tight response down to 50Hz. or so. That doesn't mean you won't hear anything below 50Hz., but it will severely tail off below that so the thump will be greatly reduced (which is what you want if you want to focus on and learn bass lines.) You can always add a subwoofer later if sometimes you just want to hear that sub-bass for some reason, but your money will be best spent putting all your budget into a good pair of medium sized bookshelfs with accurate response in the 50/60Hz. range and above.
A side benefit is if you get good medium sized studio monitors that fits the above, and you start listening without boosting frequencies with eq, especially in the bottom, your ear will eventually become trained and you'll almost guaranteed begin to prefer a "flat" sound where you can hear everything in much greater detail. It may not be as exciting as having the air sucked in and out of your lungs by excessive low bass, but that's not what we're here for. The idea is to be able to hear a defined bass line.