Here is the best summary I can muster:
XTR M970 Triple 44A 32Ti/C 22A + BB = 770g (22T = 22g, Al Bolts)
XT M770 Triple 44A 32S/C 22A + BB = 853g (22T = 22g, Al + Steel Bolts)
SLX M660 Triple 44A 32S/C 22S + BB = 889g (22T = 40g, Al + Steel Bolts)
SLX M665 Double 36A 22S + Bash + BB = 999g (22T = 40g, Al + Steel Bolts)
SLX triple is heavier than XT mostly due to a steel 22T.
SLX double+bash is a different animal.
Middleburn RS8 + Square Taper would come in at approx 820-850g, but depends on BB and the ring sizes chosen. You can even get 5-bolt-CD 20T granny.