Selling by the case and by the single from the same stock pool is where a lot of wholesale systems fall over. Break a case and the unit count drifts; price the single wrong and the margin leaks.
Case breaking and multi-level pricing (1u20134) handle this cleanly: one product, multiple selling units and price levels, with stock that stays accurate whether you move a pallet or a single. You sell however the customer buys, without losing the count.