The AVA-2906 does have internal and external connectors. It will support internal and external devices. The AVA-2906 adapter is a Fast SCSI-2 adapter that will support up to seven devices. It will transfer data at up to 10Mb/second across the SCSI bus and has an external DB25 pin connector and an internal standard 50 pin connector." [I have amended the previous item to reflect this.]
Update: An Adaptec press release confirms that the SCSI Card 2906 "supports both internal and external connections." However, Tim Norton informs me that the Mac compatible version of this card will have a slightly different designation (2906 AVH instead of 2906 AVA) and will not be out for another few weeks.