> So my desktop system is now over 7 years old and I figure it might be time to invest
> in something that can do better on the more heavy-duty games in MAME.
My current desktop system is an i7-6700K on an ASUS motherboard. It's got gobs of power for MAME and other demanding apps, but it's also an order of magnitude cooler and quieter than the heavily overclocked Sandy Bridge machine that it replaced. It UEFI dual-boots Fedora 26 and Win10.
However, the Coffee Lake i7-8700K is now shipping, which bumps things from 4 cores + HT to 6 cores + HT and has a turbo frequency of 4.7 GHz, and it fits in the same power envelope as the 6700K and 7700K. So I'd go with that and a matching ASUS board. As Haze said, their lower-end stuff is just as solid as the high-buck boards if it has the I/O you need and you don't care about overclocking. I usually end up buying some features I don't need in order to get the I/O I do need.
The 750Ti video card is fine if you won't use shader effects. If we ever do run e.g. the Voodoo emulation on the GPU as a shader (Ted has a working proof of concept written for D3D11) that will almost certainly need a beefier card.