Additional Study Information: This study is being done to answer the following questions: Do people with amyloid light chain (AL) amyloidosis respond better to a consolidation treatment that uses either one high dose of the drug melphalan plus stem cell transplant or more chemotherapy alone? Which treatment plan gives patients a better quality of life? To determine which treatment plan works better against AL amyloidosis, the study is set up to find out how good the treatments are at lowering the chance of AL amyloidosis causing problems in major organs of the body. The researchers will compare the results from each treatment group.