I'm looking into putting carpet tile in my basement with the thought that if any isolated leaks or stains occur, I can just replace a few tiles. My worry is the hard, cracked, uneven concrete. The floor has a pretty drastic slope from one side of the basement to the other. This in itself I can deal with but it's a pretty uneven surface that I think would be noticeably wavy once the carpet tile is down. There are also small cracks along the joints but I don't want to replace the whole slab.

Overall the basement is dry, so to tackle the uneven surface and cracks I was thinking about coating with self-leveling cement. Of course this won't correct the slope from one side of the room to the other but hopefully it can still be used to fill the cracks and wavyness.

I'm also looking for a solution to make the carpet tile more comfortable instead of feeling like you're still walking on concrete. Are there any padding/underlayment products that work well over concrete to give the carpet a little softness?