for guys with boats like your's,i reccomend the garmin products.these are gonna give you the most bang for your buck !!

the comob units are good for guys that are tight on space-some of the boats in the 21-22' range are a little cramped at the helm area...
another good thing about the garmin combo units is,these are preloaded with all the charts,you add a transducer and you're ready to go...if you've got a t-top and you wanna save some time,you can get the version with the internal antenna-no ruiing antenna wires-saves on the installation time...now,don't all you guys jump on me here,about what i just said concerning the antenna,truth is,the unit will work absolutlet fine under a t-top,or a hard top on a walk around boat...
here's the unit i'm talking about...

https://buy.garmin.com/shop/shop.do?cID=148&pID=8109


installation on this is a snap...