Just throwing this out there...for the price of having the subframes welded in you could buy a decent welder and weld them in yourself....and then you have a welder. Thats what I did years ago with some floor pans I needed welded in. I LOVE to weld! There are not many better places to learn to weld than under your car where no one will see it. Trust me!
I've debated that for when i install my SFC's but thought the value of having them installed was doing up on a frame machine and getting everything nice and square.
I've contacted a few local guys here to install them only to discover they intended to do them on jackstands on their back. I could do that...