This actually sounds like a case for partitioning. Partition the main table, make sure the staging table is identical (indexes, constraints, columns, etc) then to move the data from staging into main you could just add a new partition to the main table and switch that new partiton with the staging table. Metadata operation, near instant.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability