Take a look at the technology that's available and what you can actually purchase from major manufacturers, in most cases it's unrealistic for a major manufacturer to be able to completely customize your system due to volume discounts with their existing partners. You will have to purchase what the average consumer would be satisfied with, but look at the choice that you have!!!

There is a new technology available across different categories such as:

CPU Graphics
Memory (RAM)
Motherboards
Power Supplies
Storage (Hard Drives)

Our personal favorite sites to review components are:

www.tomshardware.com
www.anandtech.com
www.sharkyextreme.com
www.extremetech.com
www.xbitlabs.com
www.motherboards.org
www.techreport.com
www.hothardware.com
www.storagereview.com