It depends what kind of music you like best really. Im a bass heavy person to be honest and I just recently got the KRK R8's for Christmas. I also use them for dubstep/bass heavy music production. They do asbolute wonders. They are so loud, the sub is so deep but it doesnt mud up the mids and highs they stay nice a crisp and you can hear them over the bass at any volume even on some songs where the sub is massive like godzilla I can still hear little synths and blips so crisp over the bass. From what I read before picking mine if you like more acoustic music then get the R6's. The only setback with this is if you care most about mids/treble etc.. and less bass but still listen to music where bass is a must then most people who got the R6's also bought a separate sub.
I'm sure the bass on the r6's alone is pretty heavy but I could only imagine that set up with a nice sub down there as well. (I love bass so much I want to pick up a decent sub for my r8's
).
So basically it depends on what music you want but I definitely recommend the KRKs over anything in that price. The value is great and very fair, I actually picked up my r8s as an "open-box" version which means they were just used to demo in store and saved 50 bucks each monitor (100 total) so that was nice.
As far as an amp goes, I don't have one, I am looking right now to find one but that's mostly for my cans and IEM's. I will say this, my soundcard in my computer has some really nice built in EQ settings and depending on what I'm listening to I have found the perfect EQ match(as far as presets go) in my soundcard's settings. When I listen to dubstep/bass heavy music I put them to the DnB setting and I would say it improves overall quality by at least 30-40x not even exaggerating. When I set it to acoustic mode or rock when I'm listening to the beatles or any other classic rock (this also works with alternative) it also increases the overall quality by massive amounts.
Sorry I wrote so much just had a lot to say, So overall I definitely recommend the KRKS, whether you want the r8's or r6's it depends on the type of music you like and if you want to spend extra on a sub with the 6's or just get the 8's with no sub at all. Lastly if your computer's soundcard doesn't have nice built in EQ settings then you might want to invest in an amp, it probably doesn't have to be an expensive amp at all, just good enough to tweak around your levels to your liking as that's always better than any default, but it definitely isn't required but highly recommended.
Hope I could help!
