Drift back to the middle.
Since you own a Glock and like it, my 1st choice is the model 21, reliable, accurate and 13 + 1, even now mags are not ( wince ) too expensive. 25-30 bucks. I have had one for a long time, and it is my favorite go to, pistol, on the street, at home and in the field, not perfect, but as perfect as I can find. My next suggestion is a Para Ordnance P14, now available with 15 + 1 capacity, mine is an LDA model, limited with adjustable AO sights, I don't have big hands, but the big frame feels fine in them. I would like to play with the XD 45 and the M&P .45, but have not, You have an H&K and they make fine .45 pistols, but cost of the pistol and cost of magazines are high. They are also larger than the aforementioned, but if your familiar with them, might fit you. I think the Glock is the best fit for you, on the information you've given us. But if you just want to try something different, then the world is your oyster, but in these times, I would stick to what I'm familiar with, and can get magazines for.