It will take just a week to get use to it........u were using 145/80/R 12 a thin tyre, and now your using 155/65/13......Its not steering hardness, its your feeling of difference............. so dont worry at all, u will be use to very soon.........
And if you have enough time and 10K bucks go for Electronic power steering..........But remember............u will complain again to handle that and to get used to .............. so stick with this situation and Let your arm muscles, you will be happy