The value of a deck is that it would save wear on your camera, since the deck is used to play tapes for capture into the edit system. A much cheaper alternative is get an inexpensive HDV camera and use that as a deck, while at the same time gaining an extra camera. Canon HV20/30/40 models are cheap new or used and make a great feeder deck.
Whether looking at a deck or camera, make sure it supports your particular format. While HDV 1080i tapes should interchange with any camera or deck, some of the 24p formats are proprietary for instance.
If you work only with HDV, then a capture card is not a necessity, you just use the 1394 input on your computer. Capture cards are useful when you need to capture, output, or monitor editing via something other than 1394.
Some capture cards just add analog i/o (composite, S-video, component) as well as RCA stereo audio. Higher-end units add HMDI, SD/HD-SDI video, XLR audio, etc., depends on the needs of your studio.
An example is the Matrox MXO2 Mini. It adds HDMI and Analog i/o for PC and Mac, so you have other capture options besides 1394. Also, while editing, this product will output your timeline to an HDMI or analog monitor, so you can see your video at full size and quality, providing a better experience than just a window in the Premiere interface. Also offers some upscale/downscale options without rendering.
Jeff Pulera
Safe Harbor Computers