You’ve asked a really hard question! I’ve owned the 458s, 108 MK II and currently own the 468s.
The 468s are definitely the best- they are the total package. The 108 MK II is tonally closer to the 468s than the 458s, however, they don’t have the effortless majesty of the 458s. If your speakers are highly efficient I would save some $$ and get a 108 MK II. I don’t think used 458s are worth three times the price of a used 108 MK II. But as Mike notes, the 458s can be upgraded to 468s. A tough call that comes down to $$, as is usually the case.
Whatever decision you make, they are all incredible SS amplifiers.