If your version of Radeon HD7770 has DisplayPort, it should have two seperated, digital video output lines. Adapter should be cheap, as you convert digital DVI-D(D for Digital) to digital DisplayPort. In Poland they cost around 15 EUR, so they should cost around the same in your country. However, I don't think that HD7770 is capable of running second monitor any higher then 1080p (but I don't exclude such possibility!).
As for the second case, according to nVidia documentation:
http://www.nvidia.com/docs/IO/57865/LC_Quadro_FAM_Aug08_US_LowRes.pdf
You have both dual digital and dual analog line, so you should be capable of using 1440p monitor. Also please take a look at note in nVidia docs, that states that max. resolution of Quadro FX-770M depends on the OEM, as they can for ex. cut down max. resolution in their configs.
About additional two monitors for your mobile workstation:
I've digged through several Dell Precision related sites and most of them states that Precision series need additional dock stations (300$) for the 2nd monitor output.