If you're wanting to utilize 4 cards, you need to use an extended ATX motherboard and case which is capable of handling it.
This board in particular should handle all four cards. http://www.newegg.com/Product/Product.aspx?Item=N82E16813131802
Make sure that the case is capable of handling the extended ATX board with the spacing for the four cards (two slots each). If you want to go water cooled, it shouldn't be as much of an issue, but make sure to connect the cards together in parallel instead of serial to allow the heat to transfer better with less resistance on the pump.
Also, since you're using four cards, you'll need two power supplies to handle them. I have a Cooler Master that's capable of top and lower mounting for the PSU. Unfortunately, mounting one on the top takes away the exterior water cooling holes, but you can mount both supplies and use a cable to activate them both.
Recommend running the motherboard and two graphics cards off of the first. Then run HDD (low-power is best for this application [USB flash-drive is better as it runs off of the motherboard using ~500mw@5V]), fans and two graphics cards off of the other. Make certain that the PSUs are energy efficient so that it'll cost you less in the long-run. I perfer multiple rails as this will generally keep your power "cleaner" and your heat output down. Be careful though. I have a PSU that has a switch that puts it into multi-rail or "turbo" mode which combines all of the rails into one. It came in turbo mode by default and many people reported that the single-rail mode burned out the entire unit.
If you're extremely particular, look into purchasing a power factor correction unit for the home/office. However, if you followed my suggestion, your PSUs will already have active power factor correction built-in. They rank from bronze to silver to gold with gold being most energy efficient.
I hope this helps. ^_^
I need to know how you jumped the PSU as well. Did you only jump the power-on trigger wire or did you run the entire unit in parallel to the other? If only the trigger wire, it shouldn't have failed the way it did. This should hold especially true if you use multi-rail and different rails for each component. That would be one rail for each card, one for HDD and one for fans that aren't connected via motherboard. The motherboard should already be on its own rail if the PSU's built right.
Now some will say that multi-rail's a waste of time and money. Honestly, they don't understand what it's used for and how it decreases noise between components. But I had a DVD burner that created system noise when it was burning a disk due to the change in power usage and interfered with my CPU power causing lockups. Tossed in a multi-rail PSU and the problem was gone. I stand behind them.