Caviar Blue is not a performance drive. For the same price you might be able to get a Samsung F3 500GB.
The PSU is fine for this equipment. It wont handle expanding to a second graphics card in the future.
With an under $200 monitor you will be looking at a 1380x1050 20-22inch which will work well with a 5770. The extra $100 to jump up to a 5850 would be a better deal in price perr performance and let you run more expensive larger monitors. You have to decide what your budget can handle.