Used trolling motors sell like hotcakes. I recently sold a used Minn Kota Maxxum that I replaced with a new Fortrex.
The Fortrex was listed on FB Marketplace one evening and was claimed that same day, being picked up the next afternoon.
With your boat, you don't necessarily need an Ultrex with Spot Lock. More thrust would help to hold you in place, albeit not as convenient as Spot Lock.
Spot Lock is especially great if you fish water that's deeper than 8-10 feet regularly.
For me, I opted to install Talons on my boat instead, since the vast majority of the fishing I do is in water less than 10 feet deep. That's just my personal preference, though, while others may prefer the Spot Lock option.
For me, because I spend a lot of time in shallow lakes with lots of rocks, I would not want to have a trolling motor trying to hold me in place on a rocky flat with 10+ MPH winds blowing

I would much rather have the Talons down, holding me absolutely still, with no chances of it drifting and crashing into those boulders, destroying transducers and/or that very trolling motor that's supposed to hold me in place.