You can't upgrade to K processors in SFF machine, there is no need to upgrade power supply.  But, if you want to, you can replace the original 180w with a 240w for $13 usd.
Im going to get a Dell Optiplex 3040 SFF in a couple of weeks and I'm going to replace the Intel core i3 6100 with a intel core i7 6700K (overclocked to the most it can possibly be) and I'm going to add a AMD Radeon R7 240 2GB (overclocked to the most it can be too). Do I need a better power supply for this? If I do, can someone tell me how many watts the power supply needs to be? Or you can just send me a link to a good power supply on amazon that can hold enough power for the PC.
Re: Do I need to upgrade my power supply?