How To do a Combination by Paramters Without Needing a Nested IF

ALTER PROC [dbo].[SP_SalesReport] 
@Sheet Nvarchar(50) = NULL,
@Plot Nvarchar(50) = NULL,
@Category Nvarchar(50) = NULL,
@Type Nvarchar(50) = NULL,
@Variety Nvarchar(50) = NULL,
@Sector Nvarchar(50) = NULL,
@Owner Nvarchar(50) = NULL,
@Company Nvarchar(50) = NULL,
@Country varchar(2) = NULL,
@Statues Nvarchar(50) = NULL,
@Activity Nvarchar(7) = NULL,
@UnitPrice Decimal(18,3) = NULL,
@Week INT = NULL,
@Date DATE = NULL
AS
BEGIN

SELECT 
	Sheets.SheetNo AS 'SheetNumber',
	Plots.PlotName AS 'Plot',
	Plots.GrossArea AS 'GrossArea',
	RootStocks.RootStockName AS 'RootStock',
	Categories.CategoryName AS 'Category',
	Types.TypeName AS 'Type',
	Varieties.VarietyName AS 'Variety',
	Sectors.SectorName AS 'Sector',
	Owners.OwnerName AS 'Owner',
	CONVERT(Varchar(3),DATENAME(WEEKDAY, Sheets.Date)) + ' - '+
	CONVERT (varchar(30),
	+ DATENAME(DAY, Sheets.Date) + ' '
	+ CONVERT(Varchar(3),DATENAME(MONTH, Sheets.Date)) + ' '
	+ DATENAME(YEAR, Sheets.Date)) AS 'Date',
	DATEPART( wk, Sheets.Date) AS 'Week',
	CONVERT(VARCHAR(5), Sheets.Time,108) AS 'Time',
	Cars.CarNo AS 'Car',
	Cars.Driver AS 'Driver',
	Companies.CompanyName AS 'Company',
		(CASE WHEN Companies.CompanyActivity = 0  THEN 'Local'
		ELSE 'Export'
		END) AS Activity,
	Companies.CountryRegionCode AS 'Country',
	Representatives.RepresentativeName AS 'Representative',
	Orders.Boxes AS 'Boxes',
	Orders.QuantityKG AS 'Quantity',
	CONVERT(NVARCHAR(18),Orders.UnitPrice) + ' ' + Orders.CurrencyCode AS 'UnitPrice',
	CONVERT(Nvarchar(50),(CONVERT(DECIMAL(18,3), Orders.UnitPrice * Orders.QuantityKG)))+ ' ' + Orders.CurrencyCode AS 'TotalPrice',
	CONVERT(DECIMAL(18,3), Orders.QuantityKG / Orders.Boxes) AS 'BoxAverage',
	ExportType.TypeName AS 'ExportType',
	(CASE WHEN Orders.Statues = 0 THEN 'Paid'
		ELSE 'Pending'
		END) AS 'Statues',
	Orders.PendingPeriod AS 'PendingPeriod',
	CONVERT(DECIMAL(18,3),Orders.QuantityKG/Plots.GrossArea) AS 'AverageQuantityGArea',
	CONVERT(DECIMAL(18,3), Orders.QuantityKG/(SELECT NetArea FROM PlotDescriptionByYear WHERE PlotID = Orders.PlotID AND Season = YEAR(Sheets.Date)) ) AS 'AverageQuantityNArea',
	CONVERT(DECIMAL(18,3), Orders.QuantityKG / (SELECT PlotDescriptionByYear.NumberOfPlants FROM PlotDescriptionByYear WHERE PlotDescriptionByYear.Season = YEAR(Sheets.Date) AND PlotID = Orders.PlotID)) AS 'AverageQuantityPlantsNumber',
	CONVERT(NVARCHAR(50),CONVERT(DECIMAL(18,3),CONVERT(DECIMAL(18,3), Orders.UnitPrice * Orders.QuantityKG)/CONVERT(DECIMAL(18,3),(Plots.GrossArea)))) + ' ' + Orders.CurrencyCode AS 'AveragePriceGArea',
	CONVERT(NVARCHAR(18),CONVERT(DECIMAL(18,3),CONVERT(DECIMAL(18,3), Orders.UnitPrice * Orders.QuantityKG)/CONVERT(DECIMAL(18,3),(SELECT NetArea FROM PlotDescriptionByYear WHERE Season = YEAR(Sheets.Date) AND PlotID = Orders.PlotID)))) + ' ' + Orders.CurrencyCode AS 'AveragePriceNArea',
	CONVERT(NVARCHAR(18),CONVERT(DECIMAL(18,3), Orders.UnitPrice * Orders.QuantityKG / (SELECT PlotDescriptionByYear.NumberofPlants FROM PlotDescriptionByYear WHERE Season = YEAR(Sheets.Date) AND PlotDescriptionByYear.PlotID = Orders.PlotID))) + ' ' + Orders.CurrencyCode AS 'AveragePricePlantsNumber'
FROM
	Sheets
		INNER JOIN
	Orders ON Sheets.SheetID =  Orders.SheetID 
		INNER JOIN 
	Plots ON Orders.PlotID = Plots.PlotID
		INNER JOIN 
	PlotDescriptionByYear ON PlotDescriptionByYear.PlotID = Plots.PlotID
		INNER JOIN
	Companies ON Orders.CompanyID = Companies.CompanyID
		INNER JOIN 
	Representatives ON Orders.RepresentativeID = Representatives.RepresentativeID
		INNER JOIN 
	ExportType ON Orders.ExportTypeID = ExportType.TypeID
		INNER JOIN 
	RootStocks ON PlotDescriptionByYear.RootStockID = RootStocks.RootStockID
		INNER JOIN 
	Categories ON PlotDescriptionByYear.CategoryID = Categories.CategoryID
		INNER JOIN 
	Types ON PlotDescriptionByYear.TypeID = Types.TypeID
		INNER JOIN 
	Varieties ON PlotDescriptionByYear.VarietyID = Varieties.VarietyID
		INNER JOIN 
	Cars ON Orders.CarID = Cars.CarID
		INNER JOIN 
	Sectors ON Plots.SectorID = Sectors.SectorID
		INNER JOIN
	Owners ON Plots.OwnerID = Owners.OwnerID

WHERE PlotDescriptionByYear.Season = YEAR(Sheets.Date)
		AND (@Sheet IS NULL OR (Sheets.SheetNo = @Sheet)) AND
	(@Plot IS NULL OR (Plots.PlotName = @Plot)) AND
	(@Category IS NULL OR (Categories.CategoryName = @Category)) AND
	(@Type IS NULL OR (Types.TypeName = @Type)) AND
	(@Variety IS NULL OR (Varieties.VarietyName = @Variety)) AND
	(@Sector IS NULL OR (Sectors.SectorName = @Sector)) AND 
	(@Owner IS NULL OR (Owners.OwnerName = @Owner)) AND
	(@Company IS NULL OR (Companies.CompanyName = @Company)) AND
	(@Country IS NULL OR (Companies.CountryRegionCode = @Country)) AND
	(@Statues IS NULL OR ((CASE WHEN Orders.Statues = 0 THEN 'Paid' ELSE 'Pending' END) = @Statues)) AND
	(@Activity IS NULL OR ((CASE WHEN Companies.CompanyActivity = 0  THEN 'Local' ELSE 'Export' END) = @Activity)) AND 
	(@UnitPrice IS NULL OR (Orders.UnitPrice = @UnitPrice)) AND
	(@Week IS NULL OR ((DATEPART( wk, Sheets.Date)) = @Week)) AND
	(@Date IS NULL OR (Sheets.Date = @Date))

END