Mario - are you absolutely convinced you need to stay with the PCI type of interface?
The choices are limited with 3+ XLR inputs and PCI. You pretty much hit the only companies that provide anything in that space, in a price range you are looking for.
OTOH, USB as an interface leads to a wealth of options.
Another option is FireWire / IEEE1394 . If you go FireWire, stick with a MOBO that has a Texas Instruments chipset for the IEEE1394 controller.
I have several friends that love their PreSonus Firestudio Project interfaces.
http://www.sweetwater.com/store/detail/FireStuProj/I have a PreSonus FireBox and there are some issues with that unit. It wouldn't fit your 3+ mic input requirements however.
I guess that's something that needs clarification - when you say you want 3+ mic inputs, what exactly do you mean? Most interfaces in the sub $500 with XLR inputs have at most 2 mic pre-amps on-board. In order to use the other XLR inputs available, you would need to have outboard mic pre-amps.
Do you need the pre-amps or not? That's where a big part of the cost is tied up in the interfaces; in the mic pre-amp stages. If you have some outboard mic pre-amps that you like, then you can save some coin.
I also wouldn't say that there are necessarily better cards out there than your Creative card.
-Scott