I got a whole slew of things you can do that will unbelievably upgrade your system and will be great to do in retirement because they involve a lot of time consuming hands on. But I'm kind of close myself and can appreciate wanting to just buy something to celebrate and sort of commemorate, and a fine set of speakers sure fits the bill.
My advice with the speakers would be get whichever ones sound the best. I know that sounds cliche but a lot of people would look at the cost/value of new vs used. When the real value isn't the money its your time. You worked hard all your life. Spend the rest of it enjoying the sound you love. That might sound trite but I trust you will get it.