Has the OP considered used equipment? I don't know what the market and associated costs are when shopping from Europe, but in the US items like the Analog Discovery can be found with significant discounts. An Analog Discovery 1 just sold on ebay a couple of days ago for $130. Sure, it would cost an additional $40 for the BNC adapter and a couple of cheap probes, but it could still save $200 or more.
I don't think I would go that route for my first 4-channel benchtop scope, but for an AD I think the risk is relatively low.
Just a thought.
jason
EDIT: I haven't used any of hte scopes mentioned in this thread, but I am surprised by the high price of the Instek GDS1054B in the EU. In the US it often sells for less than the Rigol DS1054Z and the Siglent SDS1104X-U, which are closer competitors performance-wise. On paper the Siglent SDS1104X-E seems like a much better scope than the instek: dual ADCs, potential upgrades for MSO and Bode capability, more sensitive front-end (500 uV/div, versus 1 mV/div that includes some digital zoom according to the GDS1054B thread on the forums), actual BNC for the trigger out (I am pretty sure the Instek uses the probe compensation as the trigger out...), etc. Plus, if the OP already has the UniT siggen, there is a possibility that they (or someone else on the forums) will eventually figure out how to make it work with the Siglent Bode plotting.
Having said that, I thought seriously about purchasing a GDS1054B or GDS1202B for myself a number of months ago, but again I am in the US so price was a huge factor ($350 for 1054B vs $499 for SDS1104X-E; $310 for GDS1202B vs $380 for sds1202x-e). Of course that is why I am familiar with some of the quirks of the Insteks that have been posted on the forums.
jason