My first Alembic was an Epic, still have it, love it. I am very fond of the set neck, B/T tone control, sound of this model.
I too considered the East/West filter upgrade, but ended up with a Europa instead. This was followed by an SF-2 not long after.
Firstly, Since you already have an SF-2, you must be aware that it is the single coolest, most awesome and useful tone tool you can get. It will benefit ANY instrument you run through it, be it Alembic B/T, Alembic Filter and Q, or your Squier by Fender Jazz bass. In my experience, while the SF-2 can do so much more than a filter and Q onboard electronics, it can also pretty much emulate that setup as well.
In other words, a stock Epic and SF-2 can meet and surpass the performance of an upgraded Epic. But an upgraded Epic and an SF-2 can go even farther.
Secondly, if you really are certain that your Epic will be the only Alembic you EVER own, then the Filter and Q would be a nice upgrade. My advice, if it wasn't too obvious already, is to leave your Epic stock, take the money you were going to spend on the upgrade and start a fund for your next Alembic, (one with filter and Q of course).
Have fun, JBY