Cool, it would be nice if you could test 1080i deinterlacing. Regardless of the quality, if the i3 is able to do advanced deinterlacing of 1080i, it would certainly have an edge over the E-350, since the 6310 is not capable of it, according to the table you linked.
The E350 is capable of displaying stutterfree 1080i with VA de-interlacing. My system does. It is just a matter of the right settings. I can test this with Austrian TV channel ServusTV HD which is broadcasting in 1080i. Until I found the right settings it used to stutter but now it does not anymore. My System is a ASUS E35M1-M PRO mainboard with 8GB of DDR3-1333 RAM running at 1333 MHz via BIOS settings. This helps memory bandwidth for CPU and built-in AMD 6310 video adapter. Operating system is Windows 7 64 Bit. Also I am using SAF 6 with PowerDVD11 as TV Video codec and have activated VA deinterlacing via DXVAChecker. All video settings in AMD CCC are switched off execpt Dynamic Range and Manual DeInterlacing mode Vector Adaptive. Also Pull Down gets activated when selecting VA De-Interlacing.
I was planing to build my HTPC with 4 gb ram. Is it so important to have 8gb for 1080i/p playback?
And why ASUS E35M1-M PRO? there are more cheaper Mb on the market withe the same specification. For example Asrock E350M1.