i just added a new hds10 gen 2 to my 23 se cc (w/ a thru hull ducer). the unit just fits into the console box.
i'm no electronics expert - so i asked one. "what's the best combo ff/gps unit for my use?". most return questions were about my budget and what i'd be using it for as that combination seems to be the drivers in the electronics world. there are some super dooper units out there - but they are super expensive too. he basically recommended for best "real-time user bang for my buck", get the biggest screen that fit into the space available - if single combo unit, lowrance or garmin. i def wanted a single combo unit.
as i like to tow my boat and explore, a good gps/map was important. i typically fish all day in one of 3 depths; 5'-10', 30'-60', or 100'-150' deep and do really use the sonor when in deeper than 30'. he recommended the lowrance unit because he thought the gps was more or less equal but he liked the lowrance sonor better than the garmin - esp in the depths i fish. also, in general he saw less issues with lowrance units than he did with garmin units that were similar.
easy to compare prices online these days so you can see anything $ related for yourself. i was in another marine store with the gamins and the hds8 and hds10 side by side and got to play around on a lot of them. went with the lowrance and the 10 over the 8 for the very reason he suggested. its really is just easier to see and use cuz the screen is bigger. was worth the nominal price difference to me.
def would recommend you try and find a place to go play around with as many units as you can and see which one you like best.