Is Crossfire worth it versus one mega good card

FX-62 is too expensive in my book, but whatever floats your boat.

You've got it all wrong on the video cards. There are basically three or four options for anyone depending on budget these days.

Option 1: 8800 GTS or 8800 GTX. For those of you who have infinite cash. No need to SLI as a single one blows away even an x1950xtx CF setup-one is more than sufficient.
Option 2: x1950pro or x1900xt (256MB version) your choice based on availability and price, though x1950pro is preferred.
Option 3: 7600GT or thereabouts, if you can't afford a $200 x1950pro, which doesn't seem to apply in this instance.
Option 4: x800PE/x850PE (assuming one exists, sorry, not up to date on that series) or x1600pro/x1650pro maybe, though at last check the x1650pro wasn't worth it for the price.
Option 5: Wait until January 20th for the R600 to launch. Source: http://www.techreport.com/onearticle.x/11319

Option 5 may not be an option if you want it or need it now.

But that's my three cents.

Less than an 8800GTS, in 95% or greater of games/cases/scenarios.

Currently, the 8800GTX is the best performance, AND the best price per performance. 8800GTS is right on its tail. And for those who can't afford either, or just don't want to spend that much money yet (January 20th is supposedly the R600's launch date, which may or may not decrease the 8800 series prices as well, not to mention we should see some 8600s and/or 8700s before then, which will also be superior to...almost everything of the current generation), there is the x1950pro (or the x1900xt [256MB version]), depending on price and availability. x1950pro is preferred but it's not THAT much of a difference. It really depends on what games you're going to play with it, though.

If you're going AMD I don't think I'd buy anything over a 4600-they all OC decently well (i.e. FX-62 speeds)-even a 4200 might be able to pull it off (notice the might, it depends), but in all honesty C2D is a better buy right now. E6300 or E6400 if you're on a budget and depending on availability but E6600 if you're not. E6700 really isn't worth it in most places, and X6800 most certainly is not, even with the unlocked multiplier. If you've got that much cash, you'd be better off blowing it on a QX6700. Yes, blowing.

I'm no expert either, I've just done tons of research. Not nearly enough, but tons nonetheless.