<< Does this affect (some) GF4 cards only? I'm about to purchase the 8KHA+, but won't if I can't get my Radeon to fit in >>
Your Radeon will fit fine,the problem is with the GF4 Ti cards since they are longer and a capacitor that is in the way on the Epox 8KHA+ which(the board) is out of AGP spec,I`ve read one guy actually using the Visiontek GF4 TI 4600 fine on his Epox 8KHA+, it seems there are a few different Epox 8KHA+ designs out.
From HardOCP,
<< Keep in mind that we are also finding some of these same model mainboards that are allowing the VisionTek Ti4600 to be properly inserted in the AGP slot, so it is very likely that different boards were built with differing components at different times. >>