Top 10 Ways to Speed Up Your Slow Technology. I wouldn't bother overclocking any high-performance desktop GPUs.
These days they're generally factory overclocked already, and hence you probably won't be able to push them any more, and even if you can, you'll probably experience graphical artifacts (i.e snow, random pixel data getting scrambled, or more subtle problems with rendering). It may be worth trying to push a low-end GPU, or a laptop GPU (if you're sure it can handle the heat), but in the case of the latter, good luck finding a tool that works with both your laptop's chipset and GPU. I was impressed by the DNS benchmarker, but that Soluto tool you linked to is absolutely useless, at least to any real lifehacker(er). Sure, it makes some pretty graphs about your PC's status, but I already know my motherboard's model name, CPU specs, etc.
Top 10 Ways to Speed Up Your Computer's Boot Time. Speed Up Your Web Browsing in a Few Clicks: A Brief Introduction to DNS.