If you boat a lot and plan to keep the boat a while, I'd invest the money for the hardtop. Yes, as mentioned it does cost more, but it gives you shelter in all weather. When its hot, you have shade and can roll the back and sides up, when its cold, roll it all down and it will keep you warmer. It is nice to have something sturdy to grab onto. It will also add resale value and is a great selling point as well. As for mounting electronics, it will give you better singals since everything is mounted higher up. A hardtop can also give you electronics boxes for mounting more equipment if needed. It also provides a great place to place your life jackets in the webbed mesh if you opt for tjhat, well worth the saved space and the ease of retrival incase something does go wrong.
I agree, you will see a decrease in speed and fuel efficiency, but I am actually shocked by Parthery's results, almost seems like the boat was propped for a light load to begin with. You should see a 3-4mph drop in top end tops, and maybe a slight increase in fuel burn, mostly because you will run at a higher rpm to get to speeds you are used to running at. I've owned boats with and without a hardtop, and will never buy another boat without one, it is a great feature to have.
Like bob mentions, my radio boxes on my boat have a Sat phone in the one, and my Radar screen and 2 VHF radios in the other, without those boxes I would not have had enough room to mount all the electronics I wished to have, I would have had to get smaller screens or get multiscreen units, instead I have a backup to everything but my radar.
As for a GPS, Garmin is the easiest to use and have nice units, Furuno is very reliable and Northstar makes the best, but they are pricey and a little more involved to use. Raymarine units are good too, but I've heard too many issues with their units and update problems, some have been fixed but I know too many guys who bought their stuff and now are getting rid of it after being on their boats for 6 months or less. If your boat already has one brand, you may want to stick with that brand to link them all up if they are newer. Yes, most brands now link up to one another but certain brands have had some issues linking up with others, or when they do link up they do not get their full range of use that they would if linked with like brands. Not sure if adding a Radar down the road would be an option, that is something to think about as well. Furuno and Raymarine have the best radar's and northstar is not far behind. Garmin's are decent and have gotten a bit better but I'd go with one of the other's over the Gamin, the other's have been proven, the Garmin Radar's are just proving themselves now and not a ton is known about how long they will last. Also, adding XM weather is a nice touch that you may want to think about, you can overlay it on your GPS which is something I would not leave out of a new purchase if you can swing the added price tag. Always buy as big of a screen that you can afford and is sensible, I'd say 6" min, 7" or larger perfered. There are lots of good units out there, my recommendation is to go to a local electronics store and play around with them and see what you like since you will be using it. West Marine's and Boat US's are not the best stores to check, they do not carry all brands and typically their sales associates do not know about all the brands and cannot give you the best advice. Find a store near you that specializes in marine electronics as their main objective, they will give you the time to go over basics and find what suits you best. If it was going on my boat, I'd go with a furuno or Northstar unit although the Gamin unit's are tempting.
