Spikes should be GTG too and you can't argue with $15. PSA has a great price on Magpul stock kits including the tube, spring, buffer, end plate and castle nut. Haven't checked to see if they have the ACS or ACS-L. It might be worth it if you can sell your old stock/tube to recover some of the cost.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek