Boy, you have expensive tastes Mehdi!! I wish I had your dilema . . . I expect that you haven't had too many posts as most of us don't have either or both of your listed units to compare, but's just a guess on my part.
Some Differences that you might find useful:
* PHONO STAGE -- The First Sound doesn't have a phono stage whereas I believe the CAT SL1 preamps do so there is one difference depending on your requirements.
* ERGONOMICS -- The FS is dual mono meaning two volume and input selector switches vs CAT's single vol which may or may not bug you.
* POST SALES SUPPORT -- Mr. Go from First Sound has a stellar reputation for customer support. For example, he is offering a FREE modification to owners of FS Presence Deluxe MKII units to bring them up to the very latest standard (which, in relative terms, probably still pales in comparison to your Paramount Ultimate). But that is an example the dedication to customer satisfaction he offers. How does this compare to CAT post sales support?
I can't think of any other differences as both units are great I'm sure . . .
Kevinzoe
Some Differences that you might find useful:
* PHONO STAGE -- The First Sound doesn't have a phono stage whereas I believe the CAT SL1 preamps do so there is one difference depending on your requirements.
* ERGONOMICS -- The FS is dual mono meaning two volume and input selector switches vs CAT's single vol which may or may not bug you.
* POST SALES SUPPORT -- Mr. Go from First Sound has a stellar reputation for customer support. For example, he is offering a FREE modification to owners of FS Presence Deluxe MKII units to bring them up to the very latest standard (which, in relative terms, probably still pales in comparison to your Paramount Ultimate). But that is an example the dedication to customer satisfaction he offers. How does this compare to CAT post sales support?
I can't think of any other differences as both units are great I'm sure . . .
Kevinzoe