While I cannot give you legal advice in this forum, go consult with a local trademark attorney. There are too many variables to resolve in this type of forum.
THIS RESPONSE IS INTENDED TO CONVEY GENERAL INFORMATION ONLY. IT SHOULD NOT BE RELIED UPON OR TAKEN AS LEGAL ADVICE. FURTHER, THIS RESPONSE IS NOT INTENDED TO AND DOES NOT CREATE AN ATTORNEY-CLIENT RELATIONSHIP.
The key issue in trademark law is whether there is a likelihood of consumer confusion . Without knowing many more facts and details, I could not advise in a definitive way. But no lawyer could give you a guaranty that you could pursue to use your "PSU" mark in the manner proposed without violating trademark rights of others. Why run the risk (and expense) of using "PSU" when you already know that there are several other trademarks involving these letters? Remember---the more famous the trademark, the more likely it is that there will be some consumer confusion. One thing is sure---if you want to proceed with use of PSU, then you need to retain legal counsel to advise you as to the risks and benefits of doing so.
Trademarks and Domain names are not the same, they have different rights and enforcement methods.
In the example you cite: PSUinfo.com, if it is available then it is yours. If the website content refers to power supply units then you should be OK.
If the XXXXX means something else, the you need to review that permutation with a TM attorney for both domain name and contents.
USPTO Registered Patent Attorney, Master of Intellectual Property law, MBA I am neither your attorney, nor my answers or comments in AVVO.com create an attorney-client relationship with you. You may accept or disregard my free advice in AVVO.com at your own risk. I am a Patent Attorney, admitted to the USPTO and to the Florida Bar.
You deliberately do not state what your website will contain. I think you intend to infringe Penn State Univ. rights to profit off the current scandal. That is a high risk move and you better get good defense counsel ready for the "damage control" response that will be coming your way. Commentary and criticism are given latitude, and this scandal is a hot topic in the news, so you might well be able to do this is you have good legal advice. You are in San Diego, which is 9th Circuit, so get some local advice before you do this. Advice on Avvo alone will is no substitute for good specific advice. You need to get your specific intentions to an attorney in confidence.
So far, this is free to you. Until you pay a fee, I am not your lawyer and you are not my client, so you take any free advice at your sole risk. I am licensed in IL, MO, TX and am a Reg. Pat. Atty. so advice in any other jurisdiction is general advice and should be confirmed with an attorney licensed in that jurisdiction.