Since you are asking about PCI cards, I guess you are talking about the SoundBlaster PCI64. The AWE64 is an ISA card, and a look at CreativeLabs web site shows no hint of a PCI version of it. The PCI64 is one of the first PCI cards they had, and it seems to be similiar to the PCI128, but one manual available at Creative states that PCI64 has a "Creative synthesis engine", so it can be indeed very different from the PCI128 and later cards based on the Ensoniq chips, as pointed by HunterZ. Does anyone around have seen one of these babies?
If you can find a motherboard with ISA slots, you can use the AWE32 or the AWE64, which are problably the best cards I've seen for DOS games. They have real OPL3 FM/AdLib music (as the standard SB16), although they have limited memory for MIDI soundfonts. Compared with the newer cards (PCI128 and Live), which have better MIDI support but have poor emulated OPL3, they look like a better alternative for old games from the SB16 era.
You can also take a look at these threads. They have some useful information about old cards and DOS support:
Athlon 64 3200+/Asus K8V-X/1GB DDR400/GeForce FX 5700/SB Live! 5.1