Pros: How To Bulk Delete And Bulk Insert?

I have a table containing 8 million records.
I need to replace 2 million of these records with
a scaled down query that goes something like:
SELECT 1, ShareholderID, Assets1
FROM MyTable (Yields appx. 200,000 recods)
SELECT 2, ShareholderID, Assets2
FROM MyTable (Yields appx. 200,000 recods)
.
.
.
SELECT 10, ShareholderID, Assets1 + Assest2 + Assets3 + ... + Assets9
FROM MyTable (Yields appx. 200,000 recods)

Updates and cursors just seem to be too slow.

So far I have done the following, but was wondering if anyone could think of a better way.
SELECT 6 million records that don't need to be deleted into a #TempTable
Use statements above to select into same #TempTable
DROP and recreate Original Table
SELECT 6 + 2 million records INTO original table.

This seems rather convoluted. Is there a better approach? Would it be worth while to dump data to a file and use bcp / Bulk Insert


Any comments are appreciated,

-Marc