The key sticking point is going to be Netflix...I have seen many reviews of Atom and E350 builds saying that they work for everything but Netflix HD. I just built an HTPC after doing some research on this and consensus seems to be Celeron G540 is the bare minimum that you need (not sure about AMD). This build plays back everything fine, but I don't subscribe to Netflix so I can't veryify that it will work for you. Here is a very similar build to mine that comes in at $250 without Windows (I am running Ubuntu with XBMC on mine).
http://pcpartpicker.com/p/vwe2
PCPartPicker part list:
http://pcpartpicker.com/p/vwe2
Price breakdown by merchant: http://pcpartpicker.com/p/vwe2/by_merchant/
Benchmarks: http://pcpartpicker.com/p/vwe2/benchmarks/
CPU: Intel Celeron G540 2.5GHz Dual-Core Processor ($44.99 @ Amazon)
Motherboard: ASRock H77M Micro ATX LGA1155 Motherboard ($64.99 @ Newegg)
Memory: Crucial 4GB (2 x 2GB) DDR3-1066 Memory ($24.99 @ Microcenter)
Storage: Western Digital Caviar Blue 500GB 3.5" 7200RPM Internal Hard Drive ($54.99 @ Microcenter)
Case: Apex DM-387 HTPC Case w/275W Power Supply ($48.99 @ Amazon)
Optical Drive: Samsung SH-224BB DVD/CD Writer ($15.99 @ Newegg)
Total: $254.94
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-01-02 15:48 EST-0500)