kenchan

low tech way is after you blast it with WD40 or the like, use a small hammer and tap at the bolt. that usually breaks the rust free.

then put a closed wrench on the nut, use a mallet (wear goggles) and tap at the wrench real good hitting it counter clockwise. should work just as good as a small capacity impact.

also i recommend you get a 18v impact driver. 150lbs/ft is more than plenty to do most work. for heavy duty you'll want a higher capacity unit, preferrably airtools as the wrench itself is much smaller and easier to access suspension bolts, etc. i dont have air tools (due to stupid HOA rules for noise) but no issue with the 18v and breaker bars.