I got the
DS600 with a 6" screen for sale.
I just took it off the used Condenter I bought and replaced it with two C-70s and a DSM30. Very happy with the Ray fish finders.
The DS600X is a 600w system, but it sounds like you don't fish anywhere near 1000' deep so it will give you all the markings you need.
I like color machines as it's easier to distinguish the markings you get. You can also get a new 5" lowrance for around $500...
Like the X510c with a transom mounted ducer.
Lowrance X510c w 50/200 T/M ducer at BOEmarine
OOOOOOORRRRRRRRR...if you can plunk down a bit more change...get the Humming bird
797c2 SI, it's around $900 but what a machine. I don't know how deep the lake you fish are, but if it's less than 150 you can get very clear pictures of the bottom. Also the regular fish finder on it is very good also.