[Brians256]

I'll make a comment about dangerden's reservoir. I don't like it, personally.

1) It's horizontal, meaning that if it is even partially empty, it makes noise.
2) It's not big enough, so you need to monitor the fluid level more often. Remember, tygon/PVC tubing is actually not water tight. Over time, water WILL evaporate out of the system.
3) The fill mechanism is awkward. Since it is horizontal and shallow, you have to work at it to get it to full without spilling the coolant all over the computer. Too many iterations of fill res then start pump for 5 seconds to move coolant around the loop.
4) The fill point cap is air tight and a bit awkward to open/close. Airtight is BAD because over time as water leaks out the tubing, the tubing will tend to collapse. You can get around this with watertight material but it's awkward to use. The cap is opened with a quarter but it's not as convenient as a finger-accessible cap.

My preference is a tall/narrow reservoir with a big honkin cap on it. Make it about a quart in capacity. I used a 24-oz pepsi bottle at one time and the only problem I had was keeping it well sealed. Even better was a 1 qt tupperware liquid container (it looked like a quart container for milk). It was big and awkward to put inside a normal case, but it was superb at doing the job. It was VERY quiet, held a lot of reserve capacity and was extremely simple to fill because of the wide-mouth opening. That system ran for about 3 years with NO changes.