I think study that you have to pay for is similar to home renovations- you need to be careful not to over capitialise. If you were bursting to do it for interests sake and the love of the course material it may be different but it doesn't sound like the best choice for you.
I think this is a good analogy - also if you are interested in PMO and methodology stuff - I think that MBA would not feel detailed enough for you. As Veus said - I wouldn't know the university status of most people I work with - I really think it is irrelevant at this point in your career. I have worked for people before though who didn't have a uni degree and have also always wondered if it is affecting their prospects - so do understand that it does play on peoples minds. However with your level of qualifications in your field - any employer who would overlook you because of lack of degree isn't worth working for IMO.