The only advantage I see with the Falcon is the RAID option...and the advantage of RAID in gaming has yet to be proven. For more than $1500 over a similarly equiped XPS you would be a fool to get one! Especially since there will be little to no performance increase.
I have an XPS gen 2 and have had no problems for almost a year of hard gaming. The 6800 Go Ultra clocks are the same as mine....450. They do not offer the Pentium M chip which, clock for clock, blows away just about every CPU out there, including the awesome AMD FX line(single core).
Just saw this was an older thread....deadlytedly, what did you end up going with???