no. source is not really graphics intensive i think. its more of a CPU game. but seeing that your CPU owns hers, i dont see why its a problem. i play source myself on my 7600GT and 3600+ x2 with a 19inch wide and i dont run into any problems.
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5200+X2 @ 3.12Ghz | AC Freezer Pro | Gigabyte 790GX | 2 gigs OCZ Reper | Saphire HD4850 @ 700Mhz/1045Mhz | 22" Samsung
3600+X2 @ 2.6Ghz | Gigabyte 570i | XFX 7600GT SLI