i personally dont like the combo units for the main reason when you have them both going on split screen you only have half screen for both not enough detail for the sounder side of it so i have 3 seperate units on the boat how i have mine set up is my main sounder on console lowrance x125 to keep an eye on wats going on underneath whilst on the plain and a smaller x52 on the bow for when useing the leccy and a hummingbird gps on the console all 3 have large screens makes it alot easier to read, with the gps i dont think you need a top of the line gps my gps is quite old it only has built in maps but does its job just fine weather its saving a mark or getting back to the ramp in complete darkness (the only reason i got a gps is when i got lost in cowan creek at night and ended up near the heads)i dont use them to much more just a way home at night when on uncharted waters
depending on your budget will depend on wat you get wat i will say is id look at a high pixel grey sounder over a low pixel colour sounder and just a basic gps will do the job if you feel you want one they can come in handy tranducer power does not have to be huge if you not going throung the heads just depends on the depth your fishing
brands everyone will have their own but mine is lowrance great units never had any probs with mine