I was an ARC dealer for many years and have personally owned almost every preamp/line stage that they have made.
My vintage favorites:
LS5MKIII
LS5MKII
LS2BMKII
SP9MKIII
SP9MKII
SP14
SP11MKII
SP6E
My vintage favorites:
LS5MKIII
LS5MKII
LS2BMKII
SP9MKIII
SP9MKII
SP14
SP11MKII
SP6E