I'd like to keep it under 1k. Because I know I will have the expense of adding arca rails to my rifles.
Prior to carbon fiber, the most demanding professional photographers used big stout aluminum tripods often made by Gitzo, and big ball heads like the 55 mm Arca Swiss StudioBall, who originally designed the Arca plate system. I think used Gitzo tripods in the larger sizes are the best deals out there for uses where they aren’t carried or moved a lot and are as sturdy as anything available new today. If you watch eBay and search once in a while for camera shop used equipment the largest legs come up for $250ish, with $150ish being a great deal. Arca 55mm StudioBalls are often $175ish with $100 being a great deal. More modern head designs like Really Right Stuff still use the same idea, but have a wider range of motion, less weight, quick lever to tighten it down, and are 4x the price for the same quality. When a head has the number 55 or 40 in the name that’s the diameter of the ball.
The largest series 5 tripod in tall length with StudioBall is over 13 lbs. Easily the tripod I’d use for what you’re talking about. Originally used with medium format cameras, or old school big video equipment on news crews. Unfortunately there aren’t any on a quick scan of eBay, but estate sales turn them up monthly.
My favorite size for spotting scope use in and out of a vehicle is the tall series 4, which is still over 11 lbs. Nearly as steady for shooting as the series 5. I was turned onto it by a professional wildlife photographer (Art Wolfe) that used it for all his field work, including the largest lenses prior to carbon fiber coming out.
The photo is the smaller three series tripod, but it shows the StudioBall.
I just recently started shooting off tripods as well, and whatever size you get, you’ll wish it was steadier, so go big.