Try reHLDS from what i understand it uses less power and many bugs are fixed and
additional plugins can be installed which cant be installed on HLDS like anticheat plugins and many more.
reAMXX maybe you will need it maybe not. Try out your plugins if they work correctly with original AMXX if they dont work after you re-compile them then u will need reAMXX.
reGameDLL is not needed but try it.
Remember you will need to re-compile all your plugins! No matter if you switch to reAMXX or not.
You can find latest version here:
https://dev-cs.ru
More info but its old:
https://forums.alliedmods.net/showthread.php?t=264661
*All server owners which i know are using reHLDS.