I took up road cycling a few years ago on a second hand Cannonodale Caad9 bike. I am a rather fit but very inflexible 53 years old man. Usually I got neck pain after 1-1,5 hours in the saddle. In April i decided to give a bikefit a try and went to the local bikefitter in order to get advice for buying a new bike. I had to bring my Caad9 cause he hadnt any stationary "bikefit"-rig. I put on a stem riser the day before. He did the adjustment and asked me to give it a try before going into the market for a new one. I discovered I could easily go much longer - so have to say I had my breakthrough as a road cyclist this season. I signed up for a century sportive and got through it with only minor neck issues and have had a handful of other 100-150 km rides over the summer. I still want a new bike - want disc brakes and wider tires. If I start loking for a new bike the bike fitter asked me to look for a larger bike frame than many brands recommend to find the right frame and get a comfortable riding position. I am looking for an endurance carbon frame with typically Shimano105 groupset (or an alloy frame) but its very hard to find one. Been looking at Canyon Endurace 7 and CF7 model large and Cannondale Synapse 58 cm but they seem to be hard to get hold of before summer 2024. My bikefit measurements are attached. Any suggestions for a bike which a 182 cm guy can use with the 607mm stack I now use (or slightly lower)?

Not considering any of your fit data, a Specialized Roubaix in a 56cm will be 4.5 cm higher in stack than what your 56 cm Caad 9 is. A Cannondale Synapse in a 56 will be 3cm higher than your Caad. As for going bigger, at your 182cm I'd think you'd be shown in the 58 cm size of bikes by most. Or at least between a 56 and 58 cm bike. And you might try bigger still.

But the larger you go, the more stretched out you'll get and will be back in that more aero position you seem to not want. I'm not the limberest person around and I can't even get my hands halfway down my shins with my legs straight. But after I turned 55 I found I liked the more aero position on road bikes. I can ride them farther than I can on a upright sitting bike. IMO, the more upright the position the more weight you'll have on the saddle. And that'll make for a sore but after 60 miles.

this might help. https://bikeinsights.com

The Specialized Roubaix is still the king of stack, especially in larger sizes. Trek's Domane might be second.

The Litespeed Arenberg has a lot of stack.

Latest Argon18 Krypton/Pro carbon in L is 605mm stack. Reach is 395mm, so you'd have to drop in a longer stem to suit.
That stack and reach is with the standard front end setup.

Complete builds seem to be Sram options only e.g. R+A Cycles has some L models in stock.
Krypton Pro frameset-only option is available, but its rather exxy.