This card utilizes the DisplayPort 1.2 signal to do daisy-chaining of monitors. This is direct from the fine print on the product page (emphasis mine):
The AMD FirePro V3900 can support 5 HD (1920x1080) displays using AMD Eyefinity and DisplayPort™ 1.2 multi-streaming technologies (4 x 1920x1080p DisplayPort displays + 1 x DVI) and requires DisplayPort 1.2 multi-streaming-enabled monitors and/or hubs.
I suspect you could probably do four 1920x1200 monitors daisy-chained as well (the spec should allow it, but as it doesn't officially support that there's no guarantee). You should be able to do two 2560x1600 in that manner, but no more.
To do the multi-stream daisychaining, you'll either need DisplayPort hubs (supposedly these exist but I have yet to actually see one for sale!) or supported monitors - these will have a "DisplayPort out" for the upstream connection and are only just really hitting the market now. Those U2410s you have are very nice though, so I might be hard pressed to suggest you replace them with U2413s (recently announced, which should support this).
If you do have the proper hardware, it's as simple as daisy-chaining four monitors to the DisplayPort and the fifth to the DVI.