I have used Lowrance on a previous boat and found their kit to be good. When I first purchased AWOL she came with Navman kit that worked but to be honest I personally didn't like. The picture quality was very blocky (not enough pixels)
I now have a basic Raymarine A65 with a ds600 sounder. Both are good units with good picture quality but the menu system on the A65 can be a little awkward until you learn what all the buttons do. The A65 has been superseded by the A700 that looks a good bit of kit.
I would suggest that for a plotter go with a minimum 6" screen in fact the larger the screen the better, saves your eyes a bit. The sounder size is not quite so important however pixel count counts here to give a nice picture that's not to blocky.
I prefer separate units as if one unit breaks you don't loose all your electronics but thats just me. I can see as a larger dual purpose unit doing the job but would suggest if you go down this route get as large a screen as practical/affordable.
Colour or mono? no contest colour all the way, makes the picture much easier to see and decipher
I use MES electronics with Matt Sydenham being the contact. They have an office at Salterns (not always manned) and a unit on the nuffield industrial estate. Chris at Greenham regis is also very helpful their in West Quay Road Poole
Martin