http://www.boatersland.com/index.html
Always has the lowest prices, (lower than ebay) and great customer service.
Internet shopping has the drawback of returning items. You usually have to pay shipping. Can take awhile to get credit. Might not be able to return from some venders.
If you think there is a chance you might return an item, or there is a chance of high failure rate, then local Westmarine store is a good option. They pricematch most online stores, and have good selection in stock. I've bought Power pack and coils, that were in stock for my 1975 Evinrude 135hp, plus FishFinder after returning defective back to Buy.com. Westmarine pricematched lowest internet each time, and saved me a lot of time.
Cheap electronics:
http://www.rivermarinesupply.com/
(westmarine will pricematch)