If you can find the Shimano SL-R440-8 shifter set, these are Sora shifters for flat bars. Should jive with your Sora front derailleur. Another option would be a Shimano mountain FD that can handle large chainrings, if you can find one. Then you could use Shimano mountain STI shifters. I believe the top-swing XTR's have a more gradual arc to their cage to handle bigger rings. Since you haven't really explained what you're building, you might want to elaborate.
The Sachs chain and HG50 cassette will be ok with eachother and with your wheels.