Enrigonz - If you're using Ubuntu, you're on the Gnome Enviro. KDE is a better Multimedia Enviro, as it has more of "its own" MM functions - e.g, Kim for quick right-click Menu conversion between formats - JPEG-TIFF-GIF-PNG, resizing, including Custom-Resize, Compress 70-80-90% / Compress Custom, WebExport to presets, and a lot more. All just mentioned also work as Batch.
Digikam with many RAW options and processing (saves to 8 or 16 bit TIFF) - works very well in KDE. Ensure that you're using DCRAW-9.03 or later so Digikam can open and use current RAW versions. If you want to use RAW in Gimp - make sure that the DCRAW-Gimp-2.x is 9.03 or later.
Raw-Therapee is a "more conventional" RAW post-processing app, with hundreds of options, sliders, modes, etc. At present, RT-version 2.4.1 is the 'stable' version, the new version is still a work-in-progress.
Where some Linux apps don't run very new RAW versions (I had initial problems with Fuji's HS10 RAF RAW, and this was a temp solution), Linux DNGconverter (not a clone of the Adobe DNG one) - will convert RAWs to DNG.
For KDE Enviro, in the 'Bunties, Kubuntu has it, or you might try one of the Distros that uses KDE as its primary Enviro. PCLOS (PCLinuxOS) - does the KDE optimising very well. The Repository has over 12,000 Distro-Optimised applications, tools, utilities, etc, for rapid multi-installs with the GUI version of Synaptic. (apt-get does work in terminal if you want that. Type > apt-get --help < in terminal for all the options. )
I've been using PCLOS for just on 5 years, but do run other Distros - including the 'Bunties - in Virtual-Box for a look-see. You can also run Windows in V-Box to check or test things for Windows-using friends. Having a full install of XP-Pro SP3 that starts from nil to usable in 7-8 seconds, is a good time-saver.