DSC - You might find this interesting to follow up.
The ECBC and the SCAA both test and evaluate commercially available drip brewers.
ECBC tests are defined here:-
http://www.kaffe.no/certification-standards/
SCAA tests are defined here:-
http://scaa.org/?page=cert2
Both organisations approve the technivorm brewers as meeting their standards.
The ECBC also approves the the Melitta Excellence Thermo-steel (I might have that title slightly wrong as it's a clumsy translation from German.) and it's direct equivalent the Bonavita machine in the USA gets approval there by the SCAA.
It seems to me they both go about things in a very scientific way using precise measurements, so It's strange your own results from a technivorm didn't measure up.
As it happens I have both a technivorm and the Melitta thingie. Both work extremely well, probably because they have hefty (1400w) heaters compared to almost all the other domestic brewers around. Also - and it's a brilliant (not) bit of design in most other machines, that in those the tube with the hot water in often goes directly through the cold water tank.....
Got slagged off on here some time ago for even thinking of buying an auto drip machine - seems it isn't purist enough for some. So take care !
Ho hum.
Don't a lot of the commercial machines pre-boil the water in a tank up top, and then let it drip down through ? Pretty sure the Bunn machines do anyway.