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My CPU is sandwiched between a socket and a heatsink. Not very complex to set up, and it is all stock, so no mods involved.
Or did you mean you wanted to know what the entire system was, and not just the Central Processing Unit (CPU)?
Would you mind elaborating as to why you want to know what others are using? Steam gathers survey data if you are looking for statistical information.
If you want advice on building a system, the first place to start is with your budget. Once you know how much you want to spend, ask for help on these forums. It is also helpful to know what you want to do with the system. If you ask for help here, we will probably assume just gaming.