Another word of warning - most of the transmutes to 'random' items are not worth it. And there's no load/save going back in Diablo II
Even things like 6 gems plus one normal sword is not worth a plain socketed sword. If you use a magical or unique sword in this, you will still get a normal socketed longsword.
The Horadric Cube's most useful use by far is to upgrade gems to perfect gems. In my opinion, when you do get a load of perfect gems, don't exchange them for a Prismatic Amulet. Perfect Skull's and Perfect Diamond's are very good on their own...