Newbie question: dho804 is substantially cheaper than SDS804X right now. Given ones interest in bode plots, is Rigol a viable option?
While there are pros and cons for the DHO804 vs. SDS804X HD, that particular question has a clear answer: The DHO800 series cannot do automated Bode plots at all. It does not have a built-in signal generator, and Rigol does not support controlling external signal generators in any of their scopes.
In contrast, the Siglent SDS...X HD scopes can control external generators and use them to acquire Bode plots automatically. Only Siglent generators are supported off-the-shelf (and are decent value for money); there's also an open source "translation" software which lets you control some low-cost 3rd party generators.
You can also get a dedicated signal generator module for the SDS800X HD, the SAG1021I. It is connected via USB, does not have any user controls and is controlled via the scope. But I would recommend an external generator since it offers better value for money: Can be used separately and more flexibly, and most of them provide two output channels.