My Antec case has a purple snap-in module to easily accommodate a fan that sits directly in front of the HD's. The more I'm learning about case cooling, the more it makes sense to get such a fan. The questions I have are: 1. Are there fans that are designed to blow into the case, over the hd's, as well as fans that are designed to blow out, taking the air out from the case, or are they the same fans with a switch, sort of like a ceiling fan with a reversible option? 2. Is there any consensus as to which way is better -- blowing in over the hds, or out like an exhaust?

well you have to remember the airflow and basic science:

air goes front of the case to back, heat goes from bottom to top... side fans always intake to the motherboard.

fans that are designed to blow a certain way? dont think so.. just flip them around i guess and it becomes the latter, but there is one such fan that is optimised as an outake fan, mainly because it looks like swiss cheese hence more suction from inside the case out...

to answer your question, if your hdd bays are at the front, they should be blowing into the case anyways... airflow rules..

Thanks. I'd read about "intake fans" and "exhaust fans", but wasn't sure if that was a specific type of fan, or, as you pointed out, the orientation of the fan in the case.

The HDD quick-release cage of my Antec mid-tower is located in the front, directly above the front case fan. So it would appear from what you're saying that I should set it up as an intake fan, blowing the outside air onto the drives/into the case, towards the back. (NOTE: I have an Antec True Power 430W PSU situated at the top/back of the case, with 2 Sunon case fans, front/intake, rear/exhaust. There is also a second, purple fan holder in the back, above the exhaust fan, and below the exhaust PSU fan, which is currently empty.)

Yep.. B'coz usualy the PC is in the corner or on a wall right? (well, most people have em like that) and a confined space is usualy not a good place to source cold air from (and neither is puting a fan heater infront of the pc to warm your toes in winter... use your pc :hotbounce you get the jist..

Most people, depending on case design, can accomidate up to about 6 fans, plus the PSU's fan(s).. and if you have a trusty chordless drill with you, then its only limited by your imagination ...

but do remember.. the more spinny and moving things you have the more noise it can create...