A PCI-6025E is pretty close to a AT-MIO-16D. The only major difference is that the 16D has 5 digital ports (port 0 & 1 are 4-bit ports, & 2-4 are 8 bit ports), while the PCI-6025E has 4 8-bit ports. The PCI-6025E is supported by traditional DAQ, which I'm guessing is the driver you'll need to stick with. There are also several M-Series devices that are similar in functionality, but they are not supported by Traditional NI-DAQ, so you'd have to port your application to NI-DAQmx. The PCI-6025E may be a better choice for you at this time, because it is supported by both Traditional DAQ and NI-DAQmx, so you wouldn't have to change APIs immediately. I do recommend that you eventually move to DAQmx, though.
--Joe