Someone mentioned a
hand impact driver... They are wonderful if you have the room. I had trouble with the allen bolts holding my seats down. Several rounded out almost immediately as I was trying to remove them. I slotted the heads and used my hand impact driver to nudge them. I removed 4 bad ones in the span of about 15 minutes. It's maybe not so much the force as the shock that gets the bolt moving.
You don't know anyone that has a MIG? Most DIYers like me are always looking for a reason to break out the welder. It's kind of like chain saws. --Insert Tim the Tool Man grunting here--