-If you are not spending the money and no offense but the brands your mentioning means your not. Do not buy a magnifier unless it's real steel.
-100% agree DMR is a look nothing to do with barrel length.
-Most DMR style rides outside of an m16 or MK18 have proprietary parts and mags that limit your ability to upgrade for distance and consistency.
Your better off buying a higher end M4 brand and upgrading the barrel to a high end tight bore and adding an Rhop then spending a bunch of numerous guns and accessories that will not help with accuracy or consistency.