Yes an external powersupply is needed for the Dual DVB-S/S2/S2X tuner - it's required for the LNB and/or Rotor.
The Single DVB-S/S2/S2X Tuner will try to use the power available from the USB port - but there are only 2.5W available so it very much depends on the satellite system itself.
By the way 12V can also be taken from the PC system itself (eg. harddisk connector)
PCI-Express devices are in progress, we don't have them on the market yet but they will be available within the next 2 months I would say (according to the current status). Contracts with chip suppliers are signed, samples are in our office. The PCI-Express datatransfer already works, we are working on the frontend (receiver part at the moment).