I only yesterday got a Gigabyte Aorus B450 mini-ITX for ~110€ and a 3600X using the boxed cooler. Works fine, single-core boosts to 4.325GHz out of the box, which could well be down to silicone lottery. I haven't tried anything to get it higher yet, but all in all, from my initial experience and from what I've read in articles, B450 is fine for now, unless you are missing some features that are important to you like PCIe 4.0.