I bought a Ruxxac XL cart about 25 years ago. Standard fold-flat 2 wheel design with an extra long platform, bungee cord, and soft rubber tires. Never any problems with 2 Bergantino HT112 cabs + head rack (up to 120 lbs). Could do stairs and curbs though down is always easier than up. Much better made than the 2 wheelers I've seen at Home Depot, Ace or other hardware stores since. Also great for my IT day job.
Funny the looks I would get carrying my upright in with one arm (or bass guitar in a gig bag) and rolling the Ruxxac with amp rig behind me. I got so many jealous comments from fellow musicians and sound techs sweating and cursing while schlepping their Fender Twins, big Roland keyboard amps, drum sets, subwoofers, or whatever. Like they had literally never considered not lifting that heavy gear and making multiple trips to/from their vehicle. Hey folks, the wheel's been invented - get with the program!
Saved me so much time on multi-gig days, plus saved my bacon in sketchy cities at 2AM on a Saturday night, where if someone saw you loading into your trunk, what you put there could well be gone by the time you make the 2nd trip back.