I will check on case when back home from work, I have some offererings from another post (similar situation). Regarding your I/O front panel connection - there are a few choices left. First attempt to adapt the whole Inspiron 620 front panel to new case, not easy since it is not standard bay insertion, and second remove card reader and stick it somewhere, which is also a pain.
This what I found on eBay. You can see 2 panels there, on one of them you can see 4 wires coming out from card reader and your motherboard does't have front panel reader connector (plus 6 wires as mentioned by rdunnill) make 10 total, still 4 wires not accounted, this is going to be headache. Can you please meantime try to see the connections inside your case going from NUMBER 7 on my diagram and attempt to identify those wires to the best of your knowledge - this is the only holdup right now. Getting new case and moving motherboard there is relatevely easy, connecting this front panel connector is something.