That PC is old now but it’s modern equiv would run around £2K give or take.
That would get you a Ryzen 3 which would be substantially faster than mine and a RTX3070 which would crush my 2080.
With two 27” 4K screens my PC came out about the same as a MacBook Pro but is much faster on the workloads I care about and as nice the MacBook Pro screen is 2x4K is better.
Bit less portable though.
Software wise Fedora is as stable as OSX and has everything I need (I’ve been Linux as a primary dev platform since the turn of the millennium) and in fact things have never been better, pretty much everything supports Linux at least that most devs need in 2020 (Xcode is an exception).
Gnome will feel most like OSX but I prefer Cinnamon.
But do you know how much of a cost savings that is ballpark?
Also do you have a guide that you follow? I'd like to replace my Macbook Pro but I don't really know where to start.
Also is there a resource for a noob to run unit testing to if my performance is better when I'm done?