I have a 2005 nitro z6 ...right now I have some cheapo humminbirds on it. thinking of upgrading to the humminbird si was wondering if that will be money well spent or just go with a better set of normal sonars?

was looking at the hummingbird 600(but may be too small for si) series si or the 900 si.

thanks for the help guys..

Well, I have three Humminbird SI units. I sort of think it is money well spent.
I would not recommend the 698ci HD SI though, the screen is too narrow.
For a small screen model, the discontinued 798ci HD SI or 598ci HD SI are better choice since the screen is wider.
Of course BIGGER is better. The most important feature for Side Imaging is screen width. That is because the images scroll from the top to the bottom of the display and the size of displayed subjects is based on the SI Range setting.
The 900 series is way better than the 500 or 600 series.
Get the largest display model you can afford.

thanks wayne for the input!! glad I didn't go ahead and buy the small one..thanks again