What do you want from your set-up? indoor or outdoor? I think the newer ICS have metal bushings in them now for sometime.
My ICS M4,has the MA-56 upper package,Sysytma gears,top power bushings,Prometheus 6.03 (407mm) G&P crane stock with a G&P 2200 NiMah battery.This set-up runs 398 fps for me.I don't useit as much as I use to,but it's 4 years old now and still going! I have other upper cyl. set-ups (4-5) for indoor use. I don't think that drum mag will work with ICS,but if you can try one out before you buy would be awsome. The biggest problem I have with mine is finding Mags that work in it.I have a mag-clamp with two ICS Hi-caps lol. They were the only ones that worked in mine. Hope that helps some,Cheers!
Death Before Dishonor" Bleeding Black Label"