I like the Eagle units. They're made by Lowrance and offer similar
performance for less money. I have a FishMark 320 and I love it. Now they
sell the 400 for $200. At that resolution you can practically ID the
species of fish you're marking. If you already have Lowrance and you like
it, I suggest you look into either Lowrance or Eagle units and choose the
one with the options you like. Color is nice and there are several display
options available, pick the highest resolution you can get. GPS is
essential if you want to be able to find spots in open water repeatedly.
Also, many good maps have GPS coordinates, with this you can find good spots
on unfamiliar waters.

I'm going to go out on a limb here, but I think with the general level of
technology available today, you can get what you need from any manufacturer
and be happy. I stuck with one (Eagle) so that I would not have to learn
new interfaces and setting adjustments. They have been working flawlessly
for me.

Rich P