First HTPC Build - feedback please?

So, the time has finally come to ditch my old flaky media player box (a modded AC Ryan Play-on) and my Raspberry Pi (running xbian) and build a real HTPC.

My needs are around Group 3 or 4:
- have HDTV with HDMI
- want to play 720/1080p content
- content is mostly local, some streaming (wired) from my other PC
- don't anticipate any future needs for gaming, Netflix, TV tuner or audio bitstreaming
- case needs to fit my existing two 3.5" HDDs
- undecided on OS but will probably go with Windows 7 and XBMC

My budget is $375 or so (before taxes & shipping).

After much research, here's what I've specced:
Case: Silverstone Milo ML03B Black mATX
PSU: Antec Earthwatts Green Series 380W
Board: ASRock FM2A75 PRO4-M mATX
CPU: AMD A6-5400K APU
RAM: G.SKILL Ripjaws X F3-12800CL9D-8GBXL 8GB 2X4GB DDR3-1600
HDDs: existing 2TB WD Green and 1TB Seagate Barracuda (undecided on whether to get an SSD for the OS)

(Total $342, but I'm pretty sure I can lower that with end-of-year sales and/or pricematching)

- Any potential problems with this setup?
- Is 8GB RAM overkill, or should 4GB be fine for my needs?
- Does a 380W PSU sound like overkill considering I'm just doing playback and not gaming, even though I'll have two HDDs and possibly an SSD as well?

Thanks for any and all advice! It's been years since I built a system, so I'm a bit behind the times...