I have two systems, one with the ML SL3s and a second system with the Signums. It's really difficult to say which is better, I enjoy them both. You need the stands to go with the Signums. The bass is not great on either system, but it's adequate for the music I listen to.
If I had to chose only one to keep, it would be the Signums... seems that I spend more time listening to them, and they still sound great when I'm not sitting in the sweet spot. I use the same GTA tube amps on both systems.
I bought the Signums from an audio store in So Cal, when I auditioned them they were initially hooked up to SS amps. When they were connected to a pair of used 40W Golden Tube Audio monoblocks, the Signums sounded beautiful (sold me on both the speakers and the amps) so I'd recommend auditioning them with good tube amps, and carefully placed in the room according to the instructions in the manual.
I think you would do very well with either, but you'd have to audition both to determine your personel preference. Ideally, both the Signums and the SL3 should be at least 2 feet from the side walls and 3 feet from the rear wall.