Is the DHO800 much better than Siglent SDS1104X-E ??
Much better...Not.
It is definitely "better" in terms of display, UI and resolution.
On the other hand, there are features that the Rigol does not have.
I still wouldn't want to go back to the SDS1000X-E, because its successor is in the starting blocks.
Both can be hacked to bring up performance
Well...You can see it this way, I wouldn´t.
With the Rigol it is the (unofficial) bandwidth and memory depth, with the Siglent it is the (official) bandwidth and WiFi (afaik).
But that's about it.
DS1054Z have some kind good well thought UI
That might be your personal opinion.
Just watched review about DHO800 and looks a bit more complicated for newbie than DS1054Z
Phew...
The DHO currently has one of the best UIs on the affordable market, if you compare it directly with the DS1054Z (but also with the SDS1000X-E), there's a world of difference.
I wouldn't want to buy a DS1054Z or an SDS1000X-E today, given the successors of rigol and soon also siglent.