M16 DMR.

I'm currently working on picking out the parts. Now, i've gotten a good idea of brands, but I need opinions.

Currently looking at:
SHS AEG (Helical) Gears 27:1 (Torque Set)
SHS High Torque Motor
SHS V2 Selector Plate
PDI 260% AEG Spring (Assuming it allows me to shoot ~520 FPS)
Modify V2 Cylinder Head
Stock Cylinder (Polished)
Systema Area 1000 V2 Spring Guide
SHS Shims
SHS Cut off lever V2
Systema 1000 Tappet Plate
Promethesus Hard (Helical) Piston
Not sure on piston head, need help there.

Looking for a solid DMR gearbox, not sure there. I'm looking at a Raptor Mosfet or something a long those lines.

Opinions? I understand SHS is a solid brand, so I did not hesitate to overlook them.