You need to connect them the way that gets you the correct voltage for your amp. A series battery connection adds the voltages – a parallel connection keeps the voltage the same (you get twice the current capability though).

It might be a good idea to buy a cheap multimeter if you are going to experiment with stuff like this.

http://www.radioshack.com/product/index.jsp?productId=2103174

Go for a closed frame, as an open frame attracks dust, which you would want to avoid on your servers. Rittal for example creates proper racks. Use special cable holders to keep your cables out of the way, which makes it easier for you to access the hardware, but also makes sure that the cables do not block the airflow. Normally you would place the rack on a raised floor, which is ventilated below. The bottom of your rack would be partly open then to let the air come up. A big fan on top of the rack will suck the cool air coming in from below, together with the heat from the servers up and this way getting rid of it. If you do not have the funds for a raised floor or you do not have the room for it, then placing the rack on the floor normally is not a problem either, as long as the room is ventilated sufficiently. One big fan on top would be enough in this case, as heat rises anyway. Get a UPS, even a simple one will do for a start, and connect your routers and/or switches to the protection only connectors for example and your servers to the protection and power connectors, so that they will power down properly in case of a power failure. (Sorry, I do not know how to call these power connectors in English properly. Now that I think of it, I believe the correct word is "surge protection"…) A single rack is easy to cool, as long as you have a good fan on top of the rack and the room is cooled sufficiently. Some hints and tips: do not place the rack next to a fridge for example, or in a cupboard for example, do not use cables which are too long, if possible use shielded network cables (STP) instead of normal network cables (UTP), Cat. 5e cables are a minimum, better would be Cat. 6 cables to be more future proof, check the rack for dust and heat frequently, clean the filters of the rack frequently as well as dust might clutter up in the filter and this way block the incoming air. Good luck with your rack.