My opinion is that if you like the appearance of GameEx Arcade Edition combined with the straight forward configuration, then stick with it. It's a great frontend IMO.
On the other hand, if your goal also includes Software Lists and in depth configuration options for every emulator slot, then go with EVO. EVO is not as polished currently though, so some bumps along the way should be expected on items outside mainstream features until it has had the years GameEx has had to mature.
I ran early alpha's of EVO on a Q9650 along with 8GB without any noticeable issues. Obviously it runs much better on my current 6700K, but it is at the very least functional on later model Core 2 Duo based processors.
<edit> I don't know how I missed "video card", but I wouldn't think those requirements are steep at all, no more so than the MAME titles you're interested in would require. I've ran it on a GTX-750Ti and a HD-7950, they don't seem to taxed in the least.