The Nismo Stagea is an improved version of the 260RS, here is a link with some specs:
Nissan Stagea Nismo 260RS
and here are some pics of a M35 Nismo Stagea:
Stagea Nismo M35
I have been watching the stagea's that have been coming up in auctions and offered by dealers in Japan for the last couple of months, still havent seen a Nismo version for sale, have seen a few 260RS Autech's though, generally around the 40k mark (landed and complied)