RAID 5 vs. RAID 10 for HTPC

[FengPangzi]

I just picked up and HTPC case that can hold four hard drives, and I am trying to figure out the best way to configure the array.
Here are the system specs:
DFI LANParty GF9400-T2RS
Core 2 Duo CPU (model to be determined, probably an E8400)
2 x 2GB Patriot DDR2 800
2 x ATI Digital Cable Tuners
LiteOn Blu-Ray Drive
Integrated Graphics
Corsair HX620W Power Supply
Windows 7 Professional

4 x Western Digital WD500AACS 500 GB Green Drive
3Ware 9690SA-8I Hard Drive Controller

I will be using this computer as a dedicated Windows 7 Media Center, and I plan to leave it on 24/7. It will be my only cable box, blu-ray player, and will store my entire music collection in a lossless format. All that being said, I am looking for the system to be as stable as possible whilst sacrificing as little speed as possible. All that being said, two questions:
Do I need to get the battery backup unit for my RAID card?
I am leaning towards RAID5, but is there a convincing argument for using RAID 10?

Thanks in advance for any input.