I have been researching the same thing (and other things related to the Optima for that matter).
There are a few after market products out there that are being touted by the users as "a much better experience" and less expensive in the long run... fewer disposable parts.
The Sundance p/n 6540-501 (the large pleated piece) and the corresponding -502 (Microfilter) combined give you the 2 stages. Many have said just go to the 6540-488 and be done with it. Buy two and rotate them -- rinsing the one in service as often as needed (at least once a month) and cleaning it in a soak at tub water change. Each will give about a years worth of service based on normal useage.
The Filbur equivilent is FC-2780 and the Unicel is C-8325.
Hope this helps.
Has anyone swapped out the Sundance Optima "2 stage" filter design
for a singel filter? The system I am referring to has 2 separate filters, 1 that is your "standard" type and another that sits ontop of the standard one and is connected by a plastic top that screws onto the standard
I am inquiring because the smaller filter is a pain in A*&...
Thanks for any help..