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Yes an ATX PSU will fit in the MCE301. However, avoid PSUs with fans on the bottom of the PSU as they will be unable to get the aitflow that they need as they'll be attached to the top of the case.
The Silverstone SF30NT (fanless) would be a good choice - depending on what other components you have you may have to thinkg about additional cooling.
The SilentMax Semi Fanless PSU (Good but very expensive), or the Zalman ZM300B-APS