I'd ditch the video card and change the motherboard to a Nvidia based 9300/9400.
It ranks higher in the HQV tests(if you care) and having an all in one solution should reduce heat and perhaps noise. Maybe even use less power.
There has been some issues with the ATI 4550 and I don't know if they've been resolved. You can search the forums here about that.
Aside from that the only discrete card i'd get at this point would be the ATI 5000 series so you can get HD bitstreaming.
I would switch the hard drive to a Western Digital Green Drive. Should be quieter and run cooler and use less power. I have a ton of these in my server.
Nvidia Shield Android TV, 2x Roku 3's, 1st and 2nd gen chromecast, Amazon Fire TV stick 2nd gen, Apple TV 4, Vizio M602i-B3, LG OLED65B6
Retired - HTPC: Intel e6300 2.8ghz, Intel DG45ID, 2gb DDR2, Radeon 5570, MCE IR receiver, Yamaha RX-V663 receiver via HDMI, panasonic ax100u, 145" S-I-L-V-E-R painted screen,