128GB SSD for boot and 1TB for apps/data could be really nice. I wouldn't mess with raid - just more complexity and it probably won't do that much for you.
Connections will be on motherboard, usually 4-6 internal SATA connectors. Probably the SSD will sometimes benefit from 6Gb/s sata, but the traditional HDD won't. There shouldn't be a huge price difference anymore for the latest sata, I would guess.