#1 - For the TV tuner I personally use a Theater 650 Pro (PCI version) and have not had any issues using it with either MCE of MythTV.
#2 - For a graphics card, assuming you have PCI-express on that motherboard, I'd suggest the new ATI 4670 (basically a 3870). It runs very well for the price, has HDMI and 8.1 audio outs as well.
#3 - You might want to consider the 7200.11 series from Seagate for your storage. I have 4x of these in my system (500Gb each) and can barely hear them at all. Best of all, they're always one on special @ NCIX for around 60-70$.
Hope it helps!