If you are in a colder climate I would definitely recommend the heater, heated seats, and hot water shower. Underwater lights is a must as well, we do tons of surfing at night and it works awesome.
I would eliminate the Proview Mirror and get a PTM Edge mirror. The are unanimously awesome.
I think when you add the extra 2 tower speakers all they do is beef up one of the amps, otherwise, I think they are pretty standard. Make sure you speakers have forward facing lights. Some people who are really serious about their audio set up will scrap the factory stereo all together and go wet sounds, though ours with the 4 tower cans pounds good enough for us.
Let me know how your aftermarket sacs go. We are plumbing in some extra bags too on my X25.
One question: why the 6.2 in a X10? That's a 5K option you could spend somewheres else.