The 4670 was on par with the 3850 which was consider the best of the agp cards.
The 3850 could handle WoW on low settings but I was running a Pentium D (dual core p4) back then. Not sure how a p4 will handle it.
You need to be aware of the special drivers you need because the card uses an interface chip to convert the agp bus signals to the pcie signals that the actual card uses. You cant just use the regular radeon drivers. You need to always look for the Hotfix drivershttp://support.amd.com/us/kbarticles/Pages/CatalystAGPHotfix.aspx