With RAID you can only use drives of exactly the same size - practically this means multiples of the same drive to ensure there are no problems. So you would have the SSD as the boot disk with Windows installed on it, and then two 1TB Spinpoints would be in RAID 0 (displaying as one 2TB drive). You mentioned that you wanted to dual-boot Windows and Linux. Which one do you use most often, and what do you use each of them for? Obviously Windows for gaming, but is it just for gaming, with all your other tasks done in Linux? Or do you use Windows for gaming and some tasks, and Linux for others? Also, what distro are you planning to use?
Basically, you want the SSD to be for the most resource-intensive programs, and preferably the OS. The thing is, if you dual boot both OS's on the SSD (using two partitions), you won't have a lot of space for programs. I'd probably recommend installing Windows on the SSD (since Windows is more demanding than Linux). The exception here would be if you want to run any demanding Linux programs (ones that involve a lot of reading from the HDD) that could make use of the SSD, in which case I'd partition it.
Now comes the part I'm not sure about - I have no idea how easy it is to partition a RAID 0 setup for dual-booting, ie. putting Linux in one partition and leaving Windows free to use the rest of the drive. Theoretically it shouldn't be any different to doing it on a single drive, but I have no experience with Linux and RAID. What I'm planning to do with my next build is buy a separate, small and cheap drive to put Linux on, then have the SSD and two 1TB's in RAID for Windows use. Linux can read NTFS file systems, so if you need to store files on the Windows drives, you can still do that through Linux, but Windows can't read or write to partitions formatted with Linux filesystems (eg. ext4) - hence why I recommend giving Windows most of the drive space. If you don't want to buy an extra HDD for Linux, I'd recommend putting a Linux partition on the RAID drives - whatever size you need, but remember that you should err on the side of giving Windows more space. As a final point, remember to install Windows first, then Linux, it's much simpler that way.
With regards to the speed, traditional HDD's aren't fast enough to deliver 3Gb/s, let alone 6Gb/s - the 3Gb/s figure is just the maximum speed of the SATA II connection used by HDDs. Only SSDs can transfer data faster than the 3Gb/s SATA II standard, hence why the latest SSDs are designed to use SATA III (officially called the Sata 6G standard). With regards to rpm, the figure does have more meaning, but is still somewhat subjective - a modern 7,200rpm drive can be quite a bit faster than an old 7,200rpm drive, due to things such as number of platters, bigger cache, modernised design, etc. The Spinpoint F3's are fairly quick for 1TB drives, and they're comparatively cheap, hence why they get recommended a lot.
Hope that answers some questions - I'm glad my advice is helpful to you!