This makes sense actually. The my book will have a WD green sata drive inside, you can break the casing off it and you'll be left with an internal drive. I did this with my 500gb one when I needed another hard drive. You can use it through usb if need be, but this will be far slower than through sata.
The 8800gt is the same hardware as the fx3700, the only difference is the bios. So in that case, you can edit the bios to match the workstation card. Similarly the 280gtx is very similar to the fx5800, issue there is that the workstation card has more ram. This might make bios modding impossible, it'll certainly make it harder. Well worth a shot given the relative prices of the two cards. It all hinges around drivers, for the same hardware quadro drivers vastly improve performance in cad. Flashing the card is mainly a means of getting the quadro drivers to work with it. Performance improved a lot, thread is here if you're curious
http://forums.overclockers.co.uk/showthread.php?t=17995195
But yeah, Id probably turn the current external drive into an internal one. Running off my old 500gb my book now come to think about it. Performance is worse than a black drive, but for data its irrelevent
Ok, based on that spec, almost all looks good. What're you doing with case fans? I suspect the lian li comes with a load of fairly high quality ones. Does this mean you're putting two fans on the TRUE? If so, you'll want a Y fan splitter. Adding the second fan is good for a couple of degrees most times, I'd be inclined to only use one fan pushing based on the internal structure of the case. Will also save you 18 quid.
Further things you can do. Lapping the true will get you anything up to 5 degrees or so. Its fairly time consuming but well worth doing, it took quite a lot of effort for me to beat my lapped true with water.
You don't need to mount the ssd in one of the drive bays. Ive got mine attached to the back of my motherboard tray, as it doesn't get hot or vibrate you can put it anywhere. There were spare holes in the tray, so I put a screw through one of them into the mounting hole on the drive