Yep, sounds like PSU to me. How can you check it if the whole thing aint booting or getting to POST?
POST = Power On Self Test which is performed by the motherboard, this is the stage prior to the motherboard attempting to load the bios and boot. If at any point during this process the test fails the motherboard will emit a series of beeps indicating which stage of the POST it failed on.
Therefore if you are not getting any beeps it is either the motherboard or the powersupply. If you can prove the powersupply which can only really be done correctly with a volt meter - then it your next suspects would be the motherboard or the connections to the motherboard (assuming your cables are checked and proven).