Apple :: 17'' Macbook Pro - What Size Ssd

I have already figured out what i want on my 17'' macbook pro I'm going to buy except about the storage drives. I work with huge databases and after seeing the improvement other people I know have had after switching to ssd drives, (people who are running the same program(s) I do), I have decided that is what I need. But I really need help figuring out what size ssd I need to get, and whether to do something goofy like remove optical drive & replace with ssd or plug ssd in to expresscard slot(if even possible?)
details below:

I will be running windows via bootcamp, as the programs I mainly use only work on windows. I was looking at the 128gb ssd, and the 256gb ssd. I am not sure if 128gb is enough though. When I'm not working in windows I figured i could use the mac os for basic web stuff etc. and I would like to learn to use some of the mac music making programs for fun eventually, but I don't think I'd need much space for that(right?). I'm not a huge gamer, but i would also like room to throw a couple games on my pc, i mean mbp to play once in a while, and figure 2-3 games is going to take up around 20gb at least. I need my music, that's going to be like 10gb probably. And then I also need some room for some random movies and videos that I like to play in the background sometimes while I'm working. I figure that's prob around 20gb. So would 128gb drive be enough or should I go for the 256? It's a huge cost increase, but I figure, it's already costing me around 2700, so an extra 600 is worth it for being able to use it the way I want to, and I would just consider it an extra business expense. I read that windows 7 takes up around 30gb and could not find out how much space mac os takes up, so I would really like to hear from ppl with experience here.....