Graphics card - HD 6850 or HD 5850 (better), or GTX 480 (budget allowing).
Monitor - Samsung P2370
keyboard - your choice - stick to the good brands.
DVD/Blu Ray - lite on, budget allowing.
gaming desktops are never too compact. You can always de-assemble the whole thing and fit it in a box. Case is usually the bulkiest component. Keep the boxes.
Unless you are trying to break records, Crossfire or SLI may not always be the best entry choice, especially if you are playing on a 60hz refresh rate screen. Radeon5850/GTX470/GTX480 or HD5870 level cards are enough without SLI. Maybe in the future you can add another one.
I don't mean to tell you to buy that above combo. Look at the parts. I would go with Corsair power supply or Antec. OCZ...meh.