I would highly recommend *not* going SLI.
Now in particular is a bad time with ATI and NV preparing their "new" cards. Which will out perform the current ones.
I would recommend if you need to get a GPU now, a single 8800GTS. Save the rest of the money and just sell it and grab the latest range of cards a month or so after releases, when prices should be a little more stable.
I hear you.
Substitute an ASUS P5E X38 motherboard for the Striker Extreme ??