I was curious. Im seeing a lot of towers that have the PSU compartments on the bottom instead of the top of the case? Is it better to have the PSU on the bottom or there is no benefit? Also, is it better to get the Full tower that has E-ATX because I see the main reason for E-ATX is for the newer video cards to fit and have more clearance (ex. 4870x2).

Well I'm sure you know that warm air rises, so with that in mind the top and back fans tend to be exhaust fans. Meaning having the psu on the bottom means the heated air will rise to a better placed exhaust fan, meaning cooler temps. Although the cords usually have to be a bit longer to fit.

Yupp, thats why I thought it was a bad thing because the heat rises and while it rises it must pass the CPU so i thought it would add to the heat on the CPU.

I have built 2 with the antec 900 case and it work out great. Use the OCZ / PC POWER & COOLING S75QB silencer . No warm rises in my case.

Forgot to put the other PSU on the list note were the fan is on top of the psu .
http://www.ocztechnology.com/produ [...] sli_ready_

well if the psu ever gets hot enough the fan should kick in which pushes the air outside the case through the psu so it acts like an extra exhaust fan and i think its perfectly fine since many major companies are making their high end case like that

in the atx specs the psu is placed so that the psu will draw air directly of the cpu and push it out of the case so you get a exhaust fore you cpu. the problem with this is that you are drawing hot air through the psu, but this is not often a problem.

the real problem with putting a psu on the bottom of the case is that the psu is drawing in air from the ground and if your case is sitting on the floor or near that is a lot of dust, lint .... being pushed through the psu and you can't open a psu up to clean with out voiding the warranty (correct me if this is not true fore all psu's)

Most, if not all, bottom mount cases can have the psu fan facing up, in addition to down, so air can be sucked from either outside or inside the case, depending on the users preference.

Many computers, even today, have only three fans, the rear fan, a cpu fan, and a psu fan. Keep in mind the standard computer for your average guy wont need all the high powered components of a gaming/rendering machine. Thus, it saves money and effort by having the psu fan act as an exhaust, as well as cooling the psu. This target market doesn't care about overclocking or noise, they just need something cheap that works, and this design is sufficient.

However, an enthusiast cares less about price, and more about power an overclocking. An enthusiast computer will produce more heat, causing two problems. First, the psu will possibly overheat, which isn't good. Second, the psu is taking space that could otherwise be used to put more powerful, quieter fans, aiding in cooling. Keep in mind, the hotter the psu gets, the faster it will make it's fan(s) run, increasing noise, thus it is also quieter to bottom mount the psu.