I’ve owned KRK Rokit 5s for several years, and I would not buy them again. They don’t do anything better than the other speakers you’ve listed and do several things worse.
I don’t have anything bad to say about the BX-5s. I’ve heard them, and they’re decent, but I’ve never looked seriously at them because they’re not that much of a step up from KRKs, but they are a step up.
I’ve never heard Pioneer’s DJ speakers, and I don’t really care to because of my own personal bias against all things Pioneer. Give them a listen if you can.
The JBLs are generally regarded as the best speakers in that class by people on gearslutz, and my ears mostly agree with that when I’ve heard them, at least after I fixed Guitar Center’s setup (they were set too quiet compared to the other speakers in the room for a real comparison).
If I were buying in that price range today, it’d either be JBL LSRs or Tannoy Reveals. I think I like the Tannoys better, but your ears may be different.
If you can’t go listen to them in person, Here are well-recorded comparisons. Depending on how detailed you want to get, you can use something like this to do blind comparisons between them.
The way I’d do it would be to download samples for the speakers you’re considering as well as one or two of the “nicer” (read: expensive) ones. IIRC, the Event Opal recording was a bit hot, so it’s worth checking to make sure they’re actually at the same level (that will influence your decisions)…make sure you can reliably hear the differences and then “rank” them…and base your decision on price & ranking.
When I did it, the Event Opals ($3000/set) came out very clearly on top followed by the 8" Tannoys, which surprised the heck out of me…if those tests are accurate, the Tannoys represent a great bargain (though some people have complained about amplifier noise). The JBLs are no slouch either…I think I just prefer the voicing of the Tannoys.
I hope that helps…
Also, keep in mind that their room almost inarguably sounds better than yours…so the speakers will probably sound better in those recordings than they will in your room. Still…having speakers is better than not having them, and if you have to spend the money, you might as well have something that will work well and that you don’t have to re-buy as soon as (and if) you decide a nice sounding room is important to you.