Need intranet database/tool advice

My customer is prototyping reports using a variety of extracted data and distributing them via MS Access database files. Long-term these reports will be converted and accessed from the web. What DBs/dev tools would you recommend? The database includes medical/Rx claims which could run 400+ GB and will be accessed from 80+ USA locations. The reports are somewhat complex (spreadsheet-type layout, uses multiple subreports in Access version.) Any ideas, articles, etc would be appreciated.