Well most computers are towers so the heat is technically rising on the side of the heatsink so the fan pushing down actually blows the heat out the sides.
I have the TT Big Typhoon and once you get passed the installation the temps and noise is great. With the same fan on my side panel blowing on it its all good.
I have not tried the typhoon, but my Zalman is amazing. I could not get past 2.5 with my 3500 cpu, now I am at 2.7 just fine and after doing a overnight stress test will conitnue on.
I prefer to stay away from thermaltake, although i've heard good about the typhoon. Zalman would be the way to go, or take a look at some Thermalright heatsinks.
I think the Zalman is easier to install so just get that. If you have a cpu without a heatspreader you would definatly have issues because it slides left to right on my mobo if its too loose.