Well I just bought the 188 garmin plotter sounder for all of those reasons, 500w dual freq, 10 level grayscale The only charting software that will cover the sound AND the columbia for $150 not $325 or more. Just the difference in chart cost brought the Garmin in several hundred under anything else. From what I understand the depthfinder in the 188 is the same as the 240 blue. If you want to know more this url will let you do side by side comparisons of a whole bunch of garmin products even discontinued ones if you are an ebayer, You can even compare fishfinders to plotter sounders...
http://www.garmin.com/marine/compare.jsp

Also the West Marine off Fairview has everything side by side and people who know how to use all of it...
looks like I will have an apelco 230 for sale soon...