The total price of an i7 system is vastly overexagerated. Its not that much more than a LGA775 system.
Also, as l1qu1d said and I insinuated in my above post, two 9800GTX+ would beat any single card (single GPU) setup. Two 9800GTX+ is $330, and those are overclocked EVGA's, a single GTX 260 is $230.
While a single GTX 260 beats a 9800GTX+ it dosent SMASH it into oblivion or anything, so even if SLi isnt supported or scales poorly he still has something to fall back on, not to mention the awesome performance he will get with the SLi. He plays Oblivion, which can be maxed with even a single 8800GT, and the SLi 9800GTX+ setup will do very nice in Crysis.