Java seems to have a much more refined frame than Sundeal, weld beads are sanded down, machined brake bridge, profiled top/seat tube, matt finish makes it feel like a carbon frame to the touch.
The hydraulic disc brakes that come with the bike seems overkill for me, since I try to use the brakes as little as possible.
OEM deep aluminum rims are super strong, combined with narrower tires witch are lighter weight than wider tires.
I think the manufacture spec the complete bike really well for its price, the shipping cost is what's killing the value.
Buying the frameset can save you some coins, but you miss out on the nice components like hydraulic disc brakes, deep dish wheels.
There is plenty of frame & fork clearance for wider rims/tires combo.
I don't think you need to worry about clearance if you use wider tires to ride it in the mud/snow.
I did upgrade the OEM aluminum fork to a carbon Java fork... little shorter in steertube length, but I used a high rise stem to compensate.