The 2.8GHz CPU is going to be the bottleneck. MAME is almost entirely dependent on CPU power.
If your motherboard supports it, you might want to consider trying to overclock it. You'll need to get an aftermarket cooler, of course. Don't try overclocking this CPU with the stock Intel cooler.
I've seen overclocking guides that claim that you have a good chance at getting to 4.0GHz with that CPU if you disable hyperthreading and bump up the voltage a bit.
Google "Intel Core i7 860 overclock" for lots of info.
If you get the CRT fixed and you want to try GroovyMAME and CRT Emudriver, pick up an AMD Radeon HD 5000 or newer card. It's convenient if it has a VGA port for connecting to the JPAC without an adapter.
I think this card would work well (and it's fanless too)...
MSI Radeon HD 6450
$42.99 after rebate
If you want something a little more recent, this is a good choice...
GIGABYTE Ultra Durable 2 Series Radeon R7 240
GroovyMAME support forum on BYOAC