There are many good choices for monitor speakers and headphones. But no matter which you ultimately choose, I wholeheartedly recommend getting a copy of this software from Sonarworks:
https://www.sonarworks.com/referenceThis is a sound driver that can correct your speakers for your mixing room so that you hear as flat a response as possible. You can purchase their special calibrated reference mic, or you can use one of your own. I had one left over from an old Peavey VSX26 (for the built-in RTA function). Any similar calibration mic will work.
Using this software driver makes a world of difference in the quality of your output mix when using a PC and near-field monitors in less-than-acoustically-perfect rooms.
I have the Scarlett 2i2 interface, JBL LSR305 speakers and a set of Beyerdynamic DT770 Pro headphones. I purchased the Sonarworks package and calibrated my speakers to be "flat". Sonarworks comes already with built-in presets for a number of popular headphones. You can easily switch the EQ correction back and forth between your speakers and headphones.