951's 330i

Ok so like the title says, close to getting either. Well more like ready for the RB20 but might just get the RB25 instead.

Question though.
1. For a car that is going to be a DD and maybe start some drifting, should i get the 25? Or would the RB20 be enough? I am not really looking to get extreme numbers, maybe try for 300 plus to the wheels? Or untill i feel satisfied with my butt dyno lol. I've searched as much as i could by also visiting other sites for info. Just would like the feedback of someone who has experience this swap already.

2. Where can i purchase either one? I know there are vendors on here, but has anyone had any experience with them, or have found greater deals on other sites? Feedback on that would be appreciated as well.

3 If bought from a vendor, which either one sells a complete swap, what is the major differences between them? Is it just their own pricing because i have seen RB20's from 1000 to 1200. And then theres the RB25 between 1800 to 2400 before shipping on their advertised threads? Is it just plain mark up price? I know for the RB25 sometimes the difference can be whether it is a SI or SII.

4. On the Rb25det, i have read both sides saying the SI is better then the SII, and vice-versa. What is the real difference between the two besides the turbo? Or is it just all personal preference?

5. With the swaps that sell the uncut wiring, that just means i have to do the cutting and wire everything up right? But is this very hard to do? Where can i fine a wiring diagram for either swap? Or better yet, when i get started, can someone in socal help?!

Thanks to all who input on the questions asked. Hopefully i can get started on a swap very soon. By the way, i will be swapping it into a 95 s14.