There is a point where you are going to have to draw the line and only you know where that line should be drawn, but basically, the more expensive the mattress, the better it usually is. Decide what size mattress you are going to buy. If you already have a good headboard and frame, you will want to purchase the same size you have now. Consider the fact that while California King sized mattresses look delectably spacious, it is very difficult to find sheets to fit this size. If your child is very young, go ahead and spend the extra money on a really good mattress because it s really going to get used, bounced on and otherwise tested to its limits.
Some folks prefer a water bed to a conventional mattress.
There are a great many alternatives in the water bed market now, including some water beds that utilize multiple water tubes rather than one huge sack of water. When you have multiple water tubes, you can create different levels of firmness on each side of the bed. There are also air mattresses that provide this same feature. If you and your spouse prefer different bed firmnesses, this is a good alternative for you. It is always better to have a firm mattress than a soft one.