How do you Select TOP x but still get a COUNT of the whole query?

You can use COUNT(*) OVER()

SELECT TOP 20 *, 
       COUNT(*) OVER() AS TotalMatchingRows
FROM master..spt_values
WHERE type='P'
ORDER BY number

Doing two queries may work out more efficient however especially if you have narrower indexes that can be used in determining the matching row count but don't cover the entire SELECT list.