Dunno, I get 30DegC idle with system at 28DegC, it may not be the pump but something could be tweaked(cause I've got two 92mms on my HC!, I know
they can be tweaked
)...
What size is the M2 and system?, if it's 3/8 I definatly would'nt bother, if it's 1/2inch it
could'nt hurt, look for something with more head... what fans have you got running the HC?...