Yep the mk18 is exactly what i'm going for. I just got a CA RIS to replace the RAS that I had but the rail sits a little too high, higher than the rails on the receiver and theres some issue with fitment. A VFC crane stock is on the way and cqd sling plate from ebaybanned.
My flash hider that i'm currently using right now is a G&P but it doesn't have the QD notch so it stays on but the silencer rotates if you turn it. Suprisingly it does stay in place when firing though.
The m900 replica is made by SG(standard gear) that I bought off someone on ASR. Evike has it for $80 b