As for the rest of the compatibility:
Power supplies: 99% of current power supplies conform to the ATX standard. There are a few exceptions like custom supplies that hp, Dell, etc use but if you avoid buying replacement power supplies you should be fine.
RAM: RAM, in contrast to PCIe, isn't compatible between standards. If your board supports DDR3 RAM you must buy DDR3 RAM. Almost all DDR3 RAM will work with any DDR3 board but there are some caveats:
- Voltage: Older DDR3 RAM works at higher voltages than the motherboard will support and as such if you pick up a high voltage RAM it
might not work on your board. The current standard is 1.5v for DDR3 RAM. For compatibility's sake stick with 1.5V RAM. Once you get more experience and knowledge you can try your hand with higher voltage RAM for overcloking and such.
- Speed: RAM is rated at different speeds, the supported speed varies with each motherboard and CPU combination. What you have to have in mind is that RAM will work at the highest compatible speed:
- DDR3-1333 RAM on a DDR3-1600 board will work at 1333Mhz.***
- DDR3-1866 RAM on a DDR3-1600 board will work at 1600Mhz.***
Sometimes the board will default to 1333Mhz (JEDEC standard) even if it supports higher speeds and you'll have to setup the RAM speed manually (it usually involves just a couple of clicks in the bios).
*** With overclocking is possible to have a 1333 RAM working at 1600 and beyond but that is best left for later once your build skills are honed.
-ECC vs non-ECC: non-ECC RAM (the most common) should work on boards that support ECC RAM but the opposite isn't always true. Unless your board/CPU combo support ECC RAM (the CPU must support it too) AND you NEED ECC capabilities (workstations and servers are common recipients of ECC RAM) stick with non-ECC RAM.
CPU: This one somewhat complex. For CPU you have to look at a couple of things:
- Socket: You must match the socket of the CPU with the board's socket. You can't install a 775 CPU on a 1155 board for example. AM2, AM3 and AM3+ CPUs are an exception since the physical socket is similar just with different power planes so some AM2 boards can take AM3 CPUs and viceversa. For simplicity's sake stick with the same socket for the board and CPU.
- Power delivery: CPUs vary in rated power and as such you must take into account just how much power can the motherboard deliver to the CPU. There are boards that can deliver up to 95w, some others do 130w, etc, etc. You can look up the CPU support lists to determine if the CPU you'd like to buy is compatible with the board.
That being said, not every 130w board is the same, some will throttle the CPU speed if their power delivery circuitry gets overloaded. Here is a list of several AMD based motherboards that lists their power delivery phases and quality of such:
http://www.overclock.net/t/946407/amd-motherboards-vrm-info-database
