no, cause before the water in the res would also be heated too,... its fluid capacity just sitting there....
but since the heat output varies,... like your system is not always under load is it?
there would then be more "cool" water to heat,... instead of just the water in the loop.... cause it might take more then one look to cool down the water once its heated... now,.... so now there is more water to absorb heat....
i'm saying 2 celcius on average,... assuming uneven loads.. etc... like normal system usage....
if ur system is always under load and u never shut it off, it wouldn't do a thing,... and might even increase ur temps cause it might hurt flow rates a bit....