I'd suggest a Lowrance Elite TI or Hook, as Ben suggested. Being that you're in a big boat, and fishing Erie, I don't see the need for any sidescan. I have Sidescan/Structurescan on my boat and never use it on Erie. Maybe if I was up close and personal with the reefs I would use it more?
Even downscan imaging is not really necessary, not like we have a lot of submerged trees, etc.
Downscan seems to be standard on some of the nice Lowrance units - I will admit I'm partial to Lowrance since that's what most of my experience is with.

That being said, you could go with the Elite 7 TI with downscan for $700 LIST PRICE from Cabelas - I'm sure you can find it on sale somewhere. If you want a larger screen, you can go with the Elite 9 TI - and it might leave you with a little extra budget to pick up an enhanced map card for better charts.

Also, Ben mentioned networking - which it doesn't really sound like you will need so you could go with the Lowrance Hook series. Here's the Hook 9" screen with Navionics + map card, and downscan imaging, for $770 LIST price. Again, I'm sure you can shop around for a better deal but that would get you good functionality.
Lowrance Hook 9