+1 The first time I got fitted, it made such a difference. It wasn't even a terribly high-tech professional fitment, either, but it did wonders for my comfort and my ability to get power to the pedals. There's a fair amount of adjustment that can be done even without changing parts.
In a similar position, I did keep my own heavy Fuji, with some investment into the fitment, while also saving up for (and eventually getting) a blingy carbon bike. I like having the option of a bike I can pop the luggage on and just cruise/commute on, as well as the more agro road bike.
I found that I had to play with seats and pads a bit to get a setup that worked for my cooch. Going firmer with both the seat gel and the shorts pad - and narrower with the seat - actually helped greatly. It took a little investment, but I finally have a century-able setup that doesn't make my genitals hate me.