Question: First of all I just started doing barre chords after learning ordinary non-barre chords. Problem is they don't sound so well, so my question is, will training with hand grippers help me achieve this? Because I've been applying equal pressure and they still sound a bit off, only a bit off.

Answer: 
No. Simple answer. Your hands could be stronger than a weightlifter's and still not play barre chords, or any other chords, well.

Actually, hardly any finger strength is needed. Putting fingers as close as possible to the fretwire helps, accurate fingering helps, and a good action helps. If the strings are a long way above the fingerbaord, strength will help, but a better solution is to improve the action, or change guitars.

If any muscles help, it's the arm muscles, as they should be used a little as levers, using the thumb as a fulcrum point - which also doesn't need to be clamped to the neck.
I don't find those hand-grippers very effective in teaching you how to make your barre chords sound better. The truth is, a large part of getting your barre chords to sound good comes from good technique. There are quite a number of tiny details that will help you achieve a good sounding barre chord with minimal effort. Many people think that in order to get your barre chords down, you need quite a lot of strength, and that is not true at all. Remember that precision beats power. Focus on getting the details of the technique correct. 

Another thing that may be preventing you from getting your barre chords down is your guitar's set up. If your strings are too far away from the fretboard, you're going to have a really tough time getting your chords to sound good. Make sure your guitar is properly set up.