switching to SD1 or Nikon ?

Hi all

I shoot with the SD15 for one year and photography has overtaken my other hobbies, namely music and sport. As expected, I really like the grain of the pics this body takes, but I'm very limited for example in concert photography. The pics are unusable above 400iso, and when no flash is allowed and with such low light, the SD15 is, well, not at ease

I'm thinking of getting a SD1 which will allow me to keep my lenses (10-20mm, 17-50mm, 70mm, all of the three EX). On the other hand, a high end Nikon FF seems to match my needs.

I mostly shoot city and landscapes but I'm more and more interested in concert and people. Has someone ever experienced the SD1 in a concert environment ? If it would be disappointing, do you advice to keep my sigma gear on one side and get specific gear on the other side ?
Thanks for your help !
You can find a few of my work here http://500px.com/M1L0U