I use Transas Tsunamis 99. Love it. Has Tide height and stream data, etc. VERY easy interface and VERY clear charting. Have tried Maxsea and C-Map software and in my opinion are too heavy on PC resources.
I run Transas on a Pentium 2 300Mhz Panasonic Toughbook and it runs perfectly and uses 18W of power. Result.
Link to my Magellan GPS and does evrything a £2000 Raymarine set up does.
Regards,
Matt.
Look at SOBMAX, small Oz company, available via the web for very much less than most. Has some nice extras like plotting 'no go zone' and wind angles if linked to a wind instrument. Also, big plus, designed to work from large on screem buttons not menues so easy to use when its rough.