Opinions on a good GPS/FF combo?

I had planned on getting a HB SI by now, but circumstances have changed my plans till later in the year. I still need something reliable in a fishfinder/GPS combo in the $500 range. I have looked at the HB 587, 597 and the Lowrance 522. I'd like something that has SD card slot and compatible with map software. I am kinda leaning towards the Humminbirds since I plan to get a SI anyway and they can be networked. Any advice or opinions on which way to go? Again, I need it to be at or below $500.
Thanks,
SpeckWick

I would look at a HB 768 or 597 ci

Great deal here, Cabela's -- Humminbird Fishfinder 595 c Sonar/GPS Combo

Not sure if this has a card slot or not.

Its a economical get me by If you are going to upgrade to SI soon anyway.

Lowrance will have their side imaging released before summer. If you can hold off a few months, mabey the competition will bring the price down.