Hagen CO2 system
Yep, the system from Hagen is pretty much a glorified version of DIY CO2. I also have a freind that uses his own mixture of sugar/yeast/bakingsoda with the Hagen reactor/diffuser and he is very happy with it (that's a 29gallon tank, too!!) If you take this route I would expect alot of CO2!
I would agree with Bert in that if it is not cost prohibitive, Excel would probably be a less-hassle way to go (at least you won't worry about changing a fermenting mixture every couple weeks).