Since your PC is going to be on most of the time here given below is my recommendation.
For mother board there is no choice but this. You can boot into the internet, listen to music and see picture in 5 seconds that too without the usual operating system being switched on.
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For processor in order of preference.
The E8300 at 1333FSB
Second choice the E7200 at 1066FSB.
Intel Levies Heavy CPU Price Reductions - HotHardware X-bit labs - Wolfdale for Economical Enthusiasts: Core 2 Duo E7200 Review
For the screen you cannot go wrong with the Viewsonic.
16-inch ViewSonic VA1616w Widescreen LCD Monitor Unveiled in India
I could give you recommendations for other parts too but you wanted only processor and motherboard.
The screen I put in as a bonus.
Wait for this configuration if its not available where you live.