I just ordered one myself a few hours ago as they are discounted to £176 on amazon uk, and I've been going nuts for days looking at all the reviews of ones I could buy as my first digital scope
In my research, I came across something that could be relevant - that the chip most of these budget scopes use has internal memory - and budget scopes make use of that limited amount of memory instead of the manufacturer adding their own
I think you will need to get hold of a schematic of the next model up that has more memory, and the same chips, and see how the memory is implimented
However, the newer designs use better chips and the DSO5102P is an old design, so I think it will be difficult to upgrade - myself, I'm getting a USB logic analyzer for the more advanced stuff