Asia electric guns are rebrands of JG apparently,some pictures of their gearboxes on google confirm this.
So if it's JG I'd assume it's going to be their standard formula of 'Make everything sh*t except the gearbox' and from my experiences OP is right in that replacing the hop is a good idea.
SHS,Lonex,ZCI & G&G units are easy to get and good performers. For a bucking,G&G green rubbers,Lonex 70 degree,firefly,Pdi W hold and Prometheus soft are good options and proven. SHS buckings have apparently increased in quality according to some yanks.
You might want to check out a barrel to. As usual,Madbull barrels are a good bet,not the best by any means but cheap and good performance for the price. Stay away from the steel bull since they have some bad QC and machining issues. You can also have a go at polishing the barrel to unfuck some poor finish/machining prevalent. Google should show a few guides.
With the gearbox you can get away with regreasing and reshimming,re greasing is important since JG use awful earwax in their guns.