Ivan,
I can second what Dave just said- the SF-2 is around $500, used, and around $950 new. I had one, that I just purchased over the summer, and I loved it- it opened up a whole new world of tone for me, with both of my former non-Series Alembics.
Having said that, though, I would still save every penny and just go for the Series II. There are many far more experienced members, here, and some of them have chimed in with far more accurate information than myself... but if you're looking for the ultimate Alembic- the Series II won't disappoint.
My straight from the gut, instinctual reaction to my Series II is that I now have my dream bass- it delivers exactly what Alembic promises- the ultimate in tone.
Definitely keep the Persuader- you'll want a back-up, like Dave said. And from time to time, you'll enjoy the ease of the plug & play you have with the Persuader.
You can still use the mono (1/4) jack on a Series I or II, but it will be just that- Mono- so while there isn't truly a plug & play with a Series, there sort of is- only you're getting one pickup, instead of both... which is fine if you're just practicing by yourself, or noodling.
Get yourself a used Series I or II before trying out the Custom Order route- unless you're in a position to spend more $ and wait the necessary time for Alembic to create a work of art for you.
Again, if you're going to go for a Series, just go for the Series II- the price difference isn't that huge, and it's worth every penny you pay, and then some. You'll never want to touch another bass after you pick up a Series II.
I know of one killer Series II 4 that tempted even me, a Six String Slinger- Brian from the Low End bought it and posted it on the Low End site on October 20th. Just an FYI- the individual selling it was offering it for quite a low price, as S2s go, and I don't know what Brian acquired the bass for, but I'm quite sure that if he still has it, he's not going to let it go for the same price.
Check out this website and do a search for Alembic, and you should find the link- it's dated October 20th, 2009, and it's a Series II Custom in Walnut with Front Red Leds and an Omega cut. It has a longer upper horn, and really neat flamed Walnut. Great looking bass!
Here's the link:
http://www.thelowend.net/thelowend/used-basses.html Good Luck!
email me when/if you check that bass out, and let me know if it's still available and what Brian is asking. Just curious!
Peace;)
Frank
otisduo@yahoo.com