Old post but I'll reply for others.
E5 2420 really isn't up to speed with the newer alternatives available at the moment.
In terms of price per core value, LGA 2011 still has something to offer perhaps but I'd look for dual socket motherboards or not at all.
if you decide to go slightly newer, an X99 platform will likely give you better bang for buck, I've seen bundles like the one you've shown us range around 160-180 USD with 16GB DDR4 and a 10 core, 20 thread Xeon.
I have a bit of experience with these motherboards owning an X79 Huanan Zhi myself, if you don't mind navigating chinese websites to find drivers, its not too bad, but support is non existent, if you run into an issue, you're pretty much screwed. (I'm assuming the same applies for the other brands too like machinist, kllisre etc...)
If performance is your problem and you've found yourself a reliable botting strategy, it might be worthwhile to look for a VPS.
Prices have come down alot in my experience and because you'd likely be botting, you don't need to worry about where the server is located.
Good luck.