We would need to know exactly what DV6 yours is. There are a few different variants (with UMA memory and those with discrete memory for the graphics system) . Some variants are using soldered processors and thus you can’t replace it. Even if it is possible to upgrade the processor it will still not turn into a speed demon. I suggest that the best upgrade you can do is to install a solid state drive. Also, max out the RAM (upgrade to 8 gigs). Either upgrade will be helpful and will be a marked improvement. Download the service manual for your laptop from here It’ll tell you all you need to know about your computer.
Dylan Devries if you want to go and try some processor just keep in mind that your computer socket is S1g4. here is a list of compatible processors. If you really want to try something decent a Phenom II Black Edition Quad-Core would work in the same socket. Your motherboard will support it but we do not know if your BIOS does. That can become a major issue since we do not know which ones are BIOS supported. Since you are going for a custom case etc you must pay particular good attention to the cooling requirements. The greater the processing power the more heat is generated.
Again, I’d go max RAM and SSD first :-)