I was also looking for an NUC, but if you want more power, it can become very expensive.
So I did rather build myself a Mini-ITX system.
Yes, it isn't that small, but has mostly standard desktop components, except for the GFX card (low profile Geforce GT 1030) and an SFX power supply. The case is a Chieftec BT-02B-U3, that I made some modifications to it.