Success!
I ran the power for the titan fan (the one on top of the gpu) from the optical drive, no problems...then I took off the bracket and the card attaches to the vga monitor and sits fine.
The temp program I have only sees the hard drive....before it was 15c...now it is 30c, and it saw the gpu one time for a bit, and it was also nice and low, though I forget the exact number.
As far as streaming goes - if I connect via the network to a movie directly sitting on the external attached to my mac pro, it will play just fine. If I share the mac pro's library through iTunes and stream the movie, it now is watchable with a few jitters now and then. I am also now able to watch youtube, which I was not able to do at all before.
I think the solution is to you this as a server for iTunes and that way the videos will be local and will play great.
So -
I now have this cube as follows:
1.5 gig ram - 100 bucks
120 gig hard drive - already had it, took it out of an external enclosure.
1.5 Ghz CPU - 222 bucks including shipping.
Radeon 6200 256 MB video card - 90 w/shipping because I bought one pre flashed and pre taped. They are like 50 if you want to do the flashing.
titan fan for card 20 w/shipping
USB solution for speakers - already had it.
Cube price itself - 99 bucks "broken, good for parts" on ebay (not really broken, the guy was just ignorant of the problem).
Tiger (already had it)
32 in LCD TV as monitor (already had it)
Total price - 531 dollars.
So, the question is, is a g4 1.5Ghz, 1.5 RAM, 120 HD, 256 MB Video card worth 500 bucks?
Maybe not when a 600 dollar mini is 599 with Bluetooth and USB 2.
However - for a Cube, which is a collector's item since only 150k were ever made, I feel it is worth it. I had a blast tearing it apart and learning, and I also think the looks, the small form factor and the specs make it great for a HTPC. Also, with 2 fans, (at least the 2 I have) she is very quiet.
The only other thing I want to get for it is 30 bucks. It's an IR reciever and software named Mira that lets you control front row with an apple remote (of which I have an extra). This would be great for the bedroom.
With this front row setup, I feel this will be a great bedroom PC to watch video and iTunes, and also to serve up video via an attached firewire drive to the appletv in the other room.
I am very happy with this experiment! Long live the cube!