I have an 09 STX SCAB 4x4 with the factory 18 inch wheels. I'm looking at a set of wheels that are 18x9 6 backspace and 25 offset. How does this size compare to the stockers? I don't have a lift or level, will they work?

 

Your OEM wheels are 7.5 inches wide with 5.5 inches of BS so those wheels will stick out 1.5 inches farther.

 

I guess those wouldn't be a good choice then The stock wheels are all ready pushed out to the edge of the fenders.
I noticed you didn't mention anything about the offset, is that number not as much of a concern as the BS?

 

offset correlates to backspacing. here's a cheat sheet:

https://www.rsracing.com/tech-wheel.html