Thanks, just exploring options at this point and formulating a plan. There are some more urgent things that need to be done (replace some bedroom carpet, paint, couple modest kitchen & laundry items) plus the substantial cost of moving so its a project that will have to wait a little while. Just trying to get a sense of what some reasonable options might be.

Far as I am aware the largest standard gas inserts are about 33" (which is what we have currently) with glass area of around 28." I think its okay with the custom surround in our current 48" opening (though I'd prefer it a little bigger) but its too small for this space.

I am a little confused though about the use of gas fireplaces (not an "insert") in existing spaces, I've tried to read on this before but never felt I got a clarity.

We have two gas set ups in an 1910 home. One is a coal basket with the gas under it and the other is logs. Both are very old as far as when they were installed. In out last house an 1890 home we had 4 gas fireplaces. One was a stove insert like you show. Three were open with all of them having gas coal baskets. All were HOT ! and all were vented. Our current ones are vented and put out a LOT of heat. Way more than would be at all comfortable if we were to ever put on high which we never do.

Our house is considerably smaller than the one you show but I can assure you if you get a corresponding open vented log insert you will have as much heat as you could hope for. The stove insert would be unsightly given the incredibly beautiful fireplace you will have in the new house. Be sure and have the steel chase inspected and if it needs to have one or be replaced that is the first order of business.

I will post pics of our two. here in this house I don't have any of the other house. We moved 3 yr ago. c

Please do not put a stove in that fireplace. Gorgeous house!

here is just one style of insert. It is the largest industry wide they say. I have't down more searching but this gives you an idea. https://www.townandcountryfireplaces.com/product/tc54/

If it's a wood burning fireplace, you can get a gas log to insert and do not need glass covering it. That's what my sister did in her 1920's house.

Gas logs seem to be the easiest solution rather trying to muck it up with a stove or somehow making an insert fit. Most say ventless heats well but looks fake, gives off a smell, and may be problematic for air quality. While vented look good but give off little heat so neither seems ideal but there do seem to maybe be some vented logs that do a better job of heating than others?

I'll obviously get a fireplace contractor in, but can't always trust what they say and need to do own research.

That's why I posted. Our vented f/p are small compared to what you will have and believe me they put off a lot of heat. Uncomfortably high if we were to use on the highest setting. Not sure why anyone would say they don't put out heat. The non-vented are horrible and you have to have a timer on them as they can only run a certain amount of time before they are unsafe as far as air quality. I hope you will investigate and better yet visit places that have the open vented working so you can experience it.

I'm assuming the OP's fireplace is vented if it's wood burning. If so, then gas logs vented will work. They are different than the ones that are unvented. I would NEVER use the unvented ones.

Idk, but here's a houzz photo anyway --

"Inserts are engineered to fit into existing wood-burning fireplace openings and vent through existing chimney systems. Most fireplace inserts are at least 80% efficient, with some almost 99%."

Gas Fireplace Inserts · More Info

Fixed glass windows bleed into invisible edge, allowing for surround customization. Installs quickly and easily. It goes anywhere it can vent to the outside through a roof or an exterior wall. Needs no chimney hearth. Draws air from the outside-in, so there’s no drafts and no heat loss. 80 percent efficiency rating.

Direct Vent Vu Thru 3 ft · More Info

COASTROAD Hearth & Patio: One can convert from wood to gas, but not the other way (unless you are changing back to wood from gas). The technology involved when installing a solid fuel burning fireplaces is also acceptable for gas products, but not vice versa.
Now that modern fireplaces with glass or stones as burner media are popular, we have people ask us all the time if they can change out the artificial logs in their gas fireplace to something more modern. The answer is "NO".
But if you have a masonry woodburning fireplace with a working chimney, you may change over to a gas burner for convenience. Montegrappa inserts are not available in the US (yet), but STUV inserts are. None of the woodstove/insert types from either of those companies are very horizontal like the photo at the top, and many require that they are installed into a masonry fireplace. ------------------------
come up with your design first, and then see how the elements work together. This is going to sound like heresy on houzz.com, but architects and designers generally aren't very familiar with fireplace technology, so get a National Fireplace Institute certified hearth professional involved early on ( http://www.nficertified.org/pages_consumers/consumers-1.html ). We get plans every day with fireplaces that can't be built because the technology does not exist, or because they defy the laws of physics, or because the building codes won't allow it

Architects Magnus 8 years ago: "The clients wanted a "real" wood-burning fireplace without the expansion noise characteristic of prefabricated metal fireplaces. We used a modular masonry firebox/chimney and framed it with a metal."