Just my opinion, but...
If you're thinking about a route's safety in regards to POWER LINES, that is a big fat red flag with respect to altitude planning.
The margin of safety afforded by clearing a high pass by 3000-4000 feet (preferably more), allowing yourself to make a 180 to extract yourself from the high terrain, is something I am comfortable with. If you're flying an altitude capable single, that can get up to 16-18K (I'm not a Bonanza expert but I'd imagine that is doable if not heavily loaded), then in my opinion you can fly most places in the rockies safely, assuming careful consideration to weather and wind.
Also emphasize the altitude capable single.. A normally aspirated PA-28 and its altitude-averse wing will not cut it.
You won't depart KASE and cross Hagerman pass with 4000' AGL to spare in most singles, turbo or not.
But Hagerman is a plenty fine option to hop over to LXV in the right conditions. You even, ironically, follow the power lines. Because they will show you exactly where you are in the pass which is otherwise quite featureless.
It's all about training and familiarity. The folks talking about the Buena Vista to LXV valley being "narrow" got an out-loud chuckle out of me. That's one of the widest valleys in the Rockies until you get down near Alamosa. You can even be "dumb" in that valley and fly up the center of it and still be able to turn to lower terrain behind you, probably.
It's just really difficult to explain on the Internet. The "one wingspan" comment was dead on, for some terrain. Much narrower valleys and canyons.
Because you need that wingtip right up against that mountain to have enough turn radius to escape downhill if you gotta do a 180 and get out.
It's not scary or particularly dangerous to be on the proper side of a canyon for today's wind with a wingtip 100' off the trees and rocks if that's where you need to be to give yourself an "out". That's way better than not having an "out".
Mountain flying in a single is all about setting yourself up for the next "out". It makes a lot more sense after you get some instruction and do it.
All this "cross the pass high" is great. If you have something that cruises easily on up to the high teens, swell. Good choice. But you can successfully fly the passes with training down at 1000' AGL. You plan the crossing to minimize exposure time to only a short time where you have no options and work from one if those to the next.
I just happened to run across something that reminded me of Sparky today and realized how fast time flies. Coming up on four years since we lost him. I still remember texting a few people when I heard and one of them calling me back after they talked to his wife.
Sigh. Sucks. Big time.