Sure, mechanical keyboards are nice, but won't justify spending like an eighth of your budget on it. Look at this one:
PCPartPicker part list / Price breakdown by merchant
This rig offers a motherboard with an LGA1151 socket, which will be great for upgrading in the future. In the future, it'll be possible to buy an i7-6700 when it becomes cheaper for an easy upgrade. Memory still has one slot open for easy upgradeability in the future. I also slapped on an SSD, because that shit's good. It's the first thing you notice every morning as you boot your PC: "Hot damn. This Raytiger fella was right. This shit is good."
If you upgrade within like... 4 years you can simply resell your 750Ti, get an i7-6700, an extra stick of RAM and upgrade your videocard.
I personally have a mechanical keyboard (cherry mx blue users are annoying twats, cherry mx black masterrace) and I wouldn't justify spending such a large chunk of my budget on something so minor. Besides: media buttons are absolutely fantastic.