Be advised that, although Eyefinity is awesome, it is not exactly the most user-friendly of technologies. There are a lot of things to consider. You will need at least one active DP adapter (if using DVI) and a lot of old games do not work at those huge resolutions at all. In fact, even now, new games that are coming out STILL do not have native multi-monitor/ultra-widescreen support natively meaning they still need to be configured and such.
Don't get me wrong, I love Multi-monitor technologies like Eyefinity (I own an Eyefinity setup using the rig in my sig) but it is just not user friendly and therefore it is not for someone who wants to have a quick go at it expecting it to be easy to setup.
Also, I know you stated that you are playing old games, but a GT 610 could have trouble at multi-mon resolutions even with old games since its a card that is not intended for gaming really. Intel's integrated graphics would probably be nearly better lol