All the bikes the OP has linked to are entry level models, where the suspension is heavy, it will work, but won't be as effective as a higher end fork, and the forks will be in the disposable class.

If you want a quality 29er fork, the OP's budget for the complete bike would barely cover the cost of a quality fork, say a Reba(a good lower priced fork) @ Jenson USA is $585.

The suspension that the tire in a 29er gives, combined with a rigid fork is more than sufficient at the lower end of the markets, add to this that the OP wants to use the bike for mainly for commuting, and has been linking to some hybrids, where suspension is wasted.

For using the word niner to describe a 29er, Niner is a brand of bike (high end and very nice), not a descriptive of the bike type.