10,000 line import scenario limit - tools to help with large imports

My Acumatica reseller told me that the limit for a single import using either an SQL table or excel spreadsheet based import scenario is 10,000 lines. The seems a bit small given the fact I can import much larger datasets into the free version of MSSQL using and excel spreadsheet.

My question then is if that is indeed a limit, and I have over 250,000 activities to import into the CRM portion of Acumatica, is there a tool that anyone know of that can take a large excel spreadsheet of all the 250,000 activities and automatically generate smaller excel spreadsheets of no more that 10,000 lines so I can import them into Acumatica using and import scenario. Any tools or approaches that others have used to import large amounts of data that go beyond 10,000 lines would be greatly appreciated.