A couple of thoughts:
First, do you have another well-known source (say, digital). If the system is still not sufficiently warm for your taste, and you have tried the free stuff (speaker and seat placements, room tuning with furnishings and rugs, etc), then it’s not the source. I personally have found every B&W I have heard somewhat sterile, but I haven’t heard the 705.
Then, on cartridges: I’ve run a 2M Black for five years now. It was meant as a temporary cartridge while I saved for something “better”, but on a my table and arm I haven’t been persuaded to change. The stylus profile means that set-up is, well, fussy. (Thankfully I can adjust VTA precisely.) It’s unforgiving of unclean records. And I hated it when I heard it demo’d on my previous table and arm — go figure.
So I can understand curiosity to change. Before spending any money on what is a bit of a crapshoot, have you listened to the audio files of the MM comparison (including the 2M Black) that Michael Fremer ran on his site a few years back?
Good luck with your quest — Ping