RATIONALE: Drugs used in chemotherapy, such as dexamethasone, cisplatin, gemcitabine, and cytarabine, work in different ways to stop cancer cells from dividing so they stop growing or die. Combining chemotherapy with autologous stem cell transplantation may allow the doctor to give higher doses of chemotherapy drugs and kill more cancer cells. Monoclonal antibodies, such as rituximab, can locate cancer cells and either kill them or deliver cancer-killing substances to them without harming normal cells. Giving rituximab as maintenance therapy after stem cell transplantation may kill any remaining cancer cells. It is not yet known which salvage chemotherapy regimen is more effective before autologous stem cell transplantation in treating relapsed or refractory non-Hodgkin's lymphoma.