To answer your question - yes when you overclock you clock other things too. That's why it's important to have a basic understanding of overclocking - which also leads to why you want to manually set certain settings/voltages.
Before I can give you any overclocking advice you're going to have to post your specific system specs in your system specs profile. See my system specs.
Also you need to be comfortable with messing around with voltage settings in the BIOS. And be aware that settings for one person may not work for someone else - even if they have the exact system.
WIth that said you also need to have a basic understanding of what overclocking involves as you've found out that doing one thing can influence another.
Overclocking done wrong can damage/destroy your system.
Let me know.