CREATE TABLE [dbo].[MyTable]
(
	[MyUpdateDate] [datetime] NOT NULL,
	[MyStatus] [tinyint] NULL,
	[MyPKey] [varchar](17) COLLATE Latin1_General_CI_AS NOT NULL,
	... 153 other columns ...
	 CONSTRAINT [PK_MyTable] PRIMARY KEY CLUSTERED 
	(
		[MyPKey] ASC
	)
)

CREATE NONCLUSTERED INDEX [IX_UpdateDate] ON [dbo].[MyTable] 
(
	[MyUpdateDate] ASC
)

CREATE TABLE ##MyTempTable
(
	[MyPKey]	varchar(17) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
	... 157 other columns ...
	PRIMARY KEY
	(
		MyPKey
	)

)

INSERT INTO ##MyTempTable
	... 1,567,783 rows ...


INSERT dbo.MyTable
SELECT
	[MyUpdateDate] = GetDate(),
	[MyStatus] = 1,
	S.*
FROM	##MyTempTable AS S
WHERE	NOT EXISTS
	(
		SELECT	*
		FROM	dbo.MyTable AS D
		WHERE	    S.MyPKey = D.MyPKey COLLATE SQL_Latin1_General_CP1_CI_AS
	)
ORDER BY S.MyPKey

Query Plan:
|--Clustered Index Insert(OBJECT:([MyDB].[dbo].[MyTable].[PK_MyTable]), OBJECT:([MyDB].[dbo].[MyTable].[IX_UpdateDate]), 
  SET:([MyDB].[dbo].[MyTable].[MyUpdateDate] = RaiseIfNullInsert([Expr1008]),[MyDB].[dbo].[MyTable].[MyStatus] = [Expr1010],
      [MyDB].[dbo].[MyTable].[MyPKey] = [tempdb].[dbo].[##MyTempTable].[MyPKey] as [S].[MyPKey],...
|--Compute Scalar(DEFINE:([Expr1008]=getdate(), [Expr1010]=CONVERT_IMPLICIT(tinyint,(1),0)))
  |--Top(ROWCOUNT est 0)
    |--Sort(ORDER BY:([S].[MyPKey] ASC))
      |--Hash Match(Right Anti Semi Join, HASH:([Expr1013])=([Expr1012]), RESIDUAL:([Expr1012]=[Expr1013]))
        |--Hash Match(Aggregate, HASH:([Expr1013]), RESIDUAL:([Expr1013] = [Expr1013]))
        |  |--Compute Scalar(DEFINE:([Expr1013]=CONVERT(varchar(17),[MyDB].[dbo].[MyTable].[MyPKey] as [D].[MyPKey],0)))
        |    |--Index Scan(OBJECT:([MyDB].[dbo].[MyTable].[IX_UpdateDate] AS [D]))
        |--Compute Scalar(DEFINE:([Expr1012]=CONVERT_IMPLICIT(varchar(17),[tempdb].[dbo].[##MyTempTable].[MyPKey] as [S].[MyPKey],0)))
          |--Clustered Index Scan(OBJECT:([tempdb].[dbo].[##MyTempTable] AS [S]))