My first instinct was to say wait until you can spring for the HTM71 because it's a true 3-way with the tweeter located directly above a dedicated midrange driver, which in my experience helps not only with midrange clarity and dynamics but also with even sound dispersion from left to right in a room. I think the HTM72 is probably a relatively small overall improvement over your current center given its similar design configuration and size limitations. Problem is, the HTM71 costs $1400 or so, which may be over what you're willing to spend.
BUT, since you're already mixing speaker types, if I were you I'd absolutely audition an Aperion Audio Verus ll Grand Center speaker, which may be the perfect compromise for you between cost and performance. Aperion is a direct seller, which means they can offer higher quality drivers and components at a much lower price than retail brands, and they offer a true, no-risk and no cost (including shipping both ways) guarantee that lets you demo the speaker at home for I think 60 days. Read the reviews of Aperion's center speakers and I think you'll agree they're worth a listen. I think this will give you a BIG upgrade over your current center without having to spend 1400 bucks, and the free in-home demo is just a no brainer. I think you'll be absolutely thrilled with the performance of the Verus center. I'm a hardcore audiophile and pretty serious about HT as well, and I recommended this speaker to a friend of mine and it just sounds phenomenal. Give it a try -- I seriously doubt you'll return it, and you'll save a bundle for the performance you're getting. Best of luck in whatever you choose.
https://www.aperionaudio.com/collections/open-box-closeout-speakers/products/open-box-verus-ii-grand...