Hi Elmar, thanks for your request. First of, I've no real idea what your amp and speakers will sound like as a partnership with the SA7001-KI, that said, it is a rather fine source. The issue for most people would be the slightly leaner bass I'd imagine as there isn't whole lot wrong with anything else in the player.
It's fair to say that this isn't a fault and partnered with the rest of my setup is un-noticeable as the Sansui amp gives the CDP and speakers a bit more heft at the bottom end. Assuming that the balance between the Epos and Creek isn't also light then you should be fine. Of course, if a leaner but articulate bass is your preference, then you're home and dry.
Midrange is detailed and full without becoming analytical while the treble is nicely rolled off. The overall sound is one I can listen to for hours, and often do when I have the chance. Up until recently, Hi Fi world rated this as one of their picks in the magazine's contemporary classics listings and it's easy to see why. If SACD is important to you, as a number of Jazz titles are out on the format, then this is an obvious consideration.
Whether you should go for the used KI or the SA7003 is perhaps one for you. To go like for like, you'd be looking at the SA8003, which is the natural successor to the 7001-KI (Marantz dropped the "KI" suffix with the latest range) while the SA7001 was succeeded by the SA7003. I haven't had the pleasure of the either of the latest players yet so can't comment on their abilities. Personally, I'm delighted by my player, money well spent, so it's worth having a listen to it and see if it appeals to you.
As for alternatives, the Harman Kardon HD990 was a rather impressive CDP which I heard over the summer. One I'd shortlist. A good rich and beefy sound to it when partnered with Dali Ikon 5s and a Leema Pulse and Harman's impressive HK990 amp. The aforesaid Arcam, if it's available in your area, is also worth a look by all accounts.