LinuxQuestions.org - SBC Upgrade Recommendations

I appreciate this question is to a great extent be opinion-based but am interested in the opinions of those wiser than myself!

I am looking for an upgrade to my Pi3B. I need to upgrade as the result of a lack of sufficient connectivity; we need faster data rates from the Ethernet port. My "shopping list" is as follows:

Gigabit Ethernet and on-board WIFI (or USB 3.0 for the addition of a fast wireless dongle)
Will run debian, rasberrian or fedora
Equal or faster processing power to that of the RPi3B. My program will not use more than 4 cores at once.
"get-up-and-go" capability - I need to be able to focus my time on C++ development and cannot afford to spend much time getting, for example, the Ethernet working. Given my limited (non-existent) experience of building kernels etc. this means that functioning OS distros can be downloaded (the Pi process was nothing short of fantastically simple).
A small form-factor is a consideration. I would not want to go over twice the size of the Pi.
A matching GPOI connection to the SBC would be nice, so I can recycle my RPi3B hats. Even if the pin layout is not the same I can interface to the hat by re-cabling given sufficient numbers of pins. This is a low-priority.

Budget shouldn't be an issue, under £200 GBP would be nice. I have looked at the orange and banana `Pi's but am concerned about the poor support and have budget to spend on the existence of a better environment and lack of set-up time.

Thanks for any input!