my 4200Ti, 4800Ti & GeForceFX nv30 all got HUGE speed increases when i upgraded to Dx9 ... more on the 2D than 3D side of things though.
most noticeable in games that use the unreal2 engine actually, as my 4200Ti system went from 60-70fps in America's Army Online to 130fps.
Probably more a case of only accellerating those games which have already got Dx9 support, as my Dx8.1 & 7(or below) got little to no added speed.
Along with the new DetonatorFX drivers, i've got alot of games which go like a bat out of hell now - and 3D Mark i gained between 1,000-2,000 points for each of my GeForce
as for the price of the QuadroFX ... currently i only know of one company that sells them - i know there's more but i only know of one that sells the entire range.
PNY ... which is where i get mine
http://www.pny.com
they produce some sweet and very stable hardware
Within the Epic battle of the fates the Shadow and the Angel will meet. With it will harbinger the very fight of good vs evil!