Assuming that (i) the average length of the data within the two wide fields are relatively large (ie occupying most of the 4000 varchar field and is a common occurrence for that table), and (ii) there are many records, then it would be wise to create a separate table for the two columns and join back to the parent table.

Since the parent table is the one that is searched on mostly, this action will reduce the IO for queries against the parent table.

If you find that the average length of the data is realtively small, then the varchar data type will prevent the concerns that you may have regarding the creation of too many pages due to the wide fields.

Paul