Xblast is awesome. However, in my experience, many of their mods are not yet compatible with KitKat. For that reason alone I believe Gravity Box is the better option for customizing/themeing. Gravity Box has its own KitKat module, specifically for KK Roms. I use GB (KK) and XGELS to do most of my framework/system themeing. XGELS is a really cool Xposed module that lets you customize the stock GEL launcher. It has many options such as resizing icons/text, changing the color of the icon text, removing the text and removing the oh so annoying google search bar! Plus many more features. Anything beyond that I use/build Zip Themer mods. Zip Themer is one badass application that builds flashable zips that help making the modification and themeing process a lot more user friendly. If you wanna check out how affective zip themer can be, go ahead and check out the candy shop mod thread in the Nexus 5 Themes and Apps forum. It's quite possibly my favorite and most used method of themeing my phone!