Lowrance fish finders Need help

[NYSporty]

I'm looking at getting a new fish finder but my eyes are burning and I'm just a little confused on the lake version vrs the base version or the gold of the Elite5 CHIRP.

I'd like the E7 but I'm not sure about the mapping it has.
I have a DSI ducer on my boat now and the blue plug ice bag. The site seems to be some what misleading to me.
http://lr.factoryoutletstore.com/details/53416-97145/lowrance-elite-7-chirp-no-transducer.html

[NYSporty]

I don't understand why the eite5 base version is more than the lake version that comes with the transducer.
http://lr.factoryoutletstore.com/details/97115/lowrance-Elite-5-CHIRP-Gold-No-Transducer.html?category_id=53416

http://lr.factoryoutletstore.com/details/53416-97146/lowrance-elite-5-chirp-gold-83-200-455-800-khz.html

What's the best bang for the buck I'd say its the E7 right?