Ever thought of eSATA ?!?
USB3.0 is faster than PCMCIA and XpressCard, so adding it as a card will not give you full support.
Base on the description of D630 from Dell documentation, the PCMCIA is via USB interface, that means if you use a PCMCIA card to eSATA/USB3.0, the maximum speed is limited to 480Mb/s.
BTW, if there is USB3.0, I will abandon eSATA, because new power from eSATA interface.
OK, D630 has a dismountable DVD Rom, I think we may use that interface, however, I don't know what's the maximum speed of that interface.