The X-170 pushes a lot more air than a SF IV. It has a woodier, jazzier sound. However, it can get pretty aggressive and snotty with a metal bridge and a bit of overdrive.
It will tend to feed back more than a SF, due to its mostly hollow construction and medium body depth. It has a sound post inside to stiffen the top vibrations, but is otherwise hollow.
I have one, I think its a fine guitar.
A steal for one is about $1,000; fair price, around $1,200; unusual examples (such as the one you refer to) can go for $1,400 or more. The most expensive in the current market I have seen was for slightly under $2,000. But, it was a one-of-a-kind X-170.
It is probably sonically closest to a SF III as spec'ed by you.