Whats the average specs of all your builds? Is A/V really going to sap that much from your system as to make ANY game unplayable?
Those are around my specs (2.9Ghz X3 in the regular setup, 3.2Ghz X2 in the driving cab.....around $250 in each).
It took a LOT of tweaking to get California Speed to stay in the 90-100%.
I'm confident it would be unplayable with AV, automatic updates, auto restore, etc. running.
(No desire to undo all my tweaking to test it)
There have also been a couple threads where people with faster systems couldn't get CarnEvil running without sound skips.
Yet it works flawlessly for me (with a 32bit OS no less). They say they've tried tweaking everything in MAME.
I believe the difference was that I have nothing unnecessary for emulation running in the background.
Keep in mind that you built recently (as did I) and those parts weren't as cheap years ago when others built their cabs.
...and the bargain parts at that time weren't as fast.
A lot of cabs started out as a way of putting an outdated computer to use.
I built one last month using a 600mhz celeron.
That thing needed all the help it could get just to make it to the mid 80's games.
Forget about AV.