Re: I want to build a solid gaming PC
If you have an HDTV (720p or 1080p, though 1080p is highly recommended) then you can just use an HDMI cable to connect it to your PC, the 5870 has HDMI output with digital audio.
As for HDD, I don't think you need a top-of-the-line one to have a good PC. I'd rather increase CPU and RAM than waste money on an overly expensive HDD or SSD. If you're making a server or other storage intensive system then you may need these parts but for gaming most games run fine without a super fast HDD. I have a 640GB WD Caviar Black SATA III supported drive and it has no issues whatsoever loading games or copying files. It was $80 and has a 64MB cache, the best available right now.
One feature of the 5870 is Eyefinity. If you really want an awesome setup, buy 3 cheaper monitors instead of one expensive one. The Eyefinity technology supports 3 monitors on one graphics card allowing you to have a "surround screen" setup. In addition, when you're not gaming the extra screens are great to expand your desktop area. I recently purchased 3 1920x1080 Dell ST2210 monitors because they were on sale and it was definitely worth it. The monitors cost $450 total ($140 a piece + tax). I also had to buy a $20 DisplayPort to VGA adapter to run the third monitor, the other two hook up with DVI cables ($5 a piece).