if i were to get some krk monitors, would i need a sub too? and why?

Subs are not neccessary, but they definitely help yu get a more accurate mix (and feel wonderful!) .. the only music subs would not be necessary for is pop music, because 99% of radios dont have subs on them so subbass is worthless.

Some monitors might be designed specifically to only work with subs, but I dont think that is the case with KRK.

What I would say is this..

At first It is better to get 2 larger speakered monitors (at least 6-8" main speaker) than 2 smaller ones + a sub.. because the area just above the sub level will have a hole if you only have tiny monitors, and you wont ever be able to fix this except by buying new monitors.

Now for the sub business - regardless of if you will buy a sub or not right away,try out the ones that are designed for optional use with a sub so that if you do get a sub it will match the monitor response well - Listen to them both with the sub and without it (and listen to just the sub with no main speakers too if you can..) - pay attention to short punchy attacks - poor subs are very slow to stop/start so everything sounds blurry. also listen for boomy rattling.. poor enclosure can cause this..


One other tip..
if/when you get a sub.. set it to the level you think is right, then halve the sub's volume. I always, always, always end up with too much sub even if i try to conservatively set it by ear!

holy shit thanks man!