Subarus are tuff little vehicles. I owned 2 of them for a total of 10 years but they will lack power a lot with bigger tires. On your s10, you need a serious set of gears with bigger tires 2.8 or 2.8. You just cannot put bigger tires and them and expect them to do well unless you regear them. How deep depends on tires size but if you gear it prtoperly it will do a lot better.

You can re gear them and you can swap out engines from other subarus some have h6 2.2 and 2.5 sti engines swapped into them already and when lifted 6 inches and above transfercases are swapped in and it will give you rear wheel drive  

Mine does just fine with 26.5 inch tires and that is a 4 inch increase of tire  

Dang, way to dig up an old thread! lol