>>Can you use dynamic SQL in your query? This way you can parameterize Top.
>
>I considered it, but am a little shy to use dynamic SQP because of the traffic that this SPROC will get (on the order of hundreds of hits per second). Wouldn't dynamic SQL require that the statement be compiled on every hit? That would be unacceptable...

PMFJI,
You can use a "parameterized" sp_executesql string that could be compiled only once: (this example from the BOL):

DECLARE @IntVariable INT
DECLARE @SQLString NVARCHAR(500)
DECLARE @ParmDefinition NVARCHAR(500)  

/* Build the SQL string once. */
SET @SQLString =  N'SELECT * FROM pubs.dbo.employee WHERE job_lvl = @level'

/* Specify the parameter format once. */
SET @ParmDefinition = N'@level tinyint'

/* Execute the string with the first parameter value. */
SET @IntVariable = 35
EXECUTE sp_executesql @SQLString, @ParmDefinition, @level = @IntVariable

/* Execute the same string with the second parameter value. */
SET @IntVariable = 32
EXECUTE sp_executesql @SQLString, @ParmDefinition,
                      @level = @IntVariable

The BOL states that the query optimizer "should" use the execution plan from the first call, whatever that means. I guess testing should give you a definitive answer.

There's another bit about reusing execution plans in the BOL topic "Using sp_executesql".
HTH