what would be a compatible replacement for a bestec atx-300-12eb3 rev sr2 power supply unit?

My current Power Supply Info �Gateway Power Supply with 24 Pin Motherboard Connector �Mfgr’s Model Number – Bestec ATX-300-12EB3 Rev SR2 �P/N – 6506054R, 6506055R, 6506056R are interchangeable �300 Watt Output Would this be interchangable with either of these? DYNEX- 400-Watt ATX CPU Power Supply �400-watt power supply �ATX 12V v2.2 compliance �Compatible with Intel® [...] http://bit.ly/qy46al