I do extract brewing on the kitchen stove and find there's two problems.
1) If I try to do a full boil in one pot, I get some scorching that leaves a burnt taste in the final product.
2) If I do a partial boil and add water in the bucket, I get what I think is the "extract twang" flavor often mentioned on the forum.
Additionally, it's hard to boil 5 gallons on the electric stove top and you end up losing a lot to evaporation anyway.
So, I've found the following acceptable solution. Since all of the extract does not need to boil a full 60 minutes, I do 1-2 lbs in about 3.5 gallons of water in my 5 gallon stainless steel pot (leaves room for hops and avoids boilover). While that's going, I dissolve the remaining extract in a 3 gallon pot with the remaining water (what would have been my "top off" water). I boil this pot for 10 minutes near the end of the 60 minute boil. I add as much of it as possible to the bigger "main" pot for cool down.
Even so, I still end up about 1/2 gallon short, so the night before, I fill a clean, sanitized growler with filtered, boiled water and put it in the fridge. I use only this amount for top off to minimize "twang", and it also helps to bring down the temperature during cool down.
This method eliminates scorching, twang and let's me get a good boil going on the stovetop. It can get a little hectic and silly looking when I'm rotating pots around burners (I keep a 3rd smaller pot going to boil small amounts of water), but I'm satisfied with the results.