can i expect good performance for this combination =d80+tamron17-50mm+sigma dg super for indoor shooting?

Question

wants to shoot indoor parties and portraits

Answer 1

* The D80 essentially provides all the goodness of the D200 minus the industrial build strength. It's a very nice camera.
* The Tamron 17-50 is great value for money. The image quality is almost as good as the Nikon 17-55 f/2.8. The Nikon focusses a touch faster and is has better build quality. For social events, the wide end of the zoom is quite sufficient and at the long end you effectively have 75mm (after the 1.5 focal length multiplier) so you're okay for portriats. In time, you could add a (Sigma?) 70-200 f/2.8.
* The Sigma EF-500 Super if a bit iffy. It does support iTTL metering (unlike the 'regular' EF-500) and with the included wide-angle panel it also supports the full zoom range of your intended lens, but I'd recommend the Nikon SB600 instead. The SB600 seems to just work better. Perhaps the biggest attraction of the SB600 is its faster recycle time: just 2.5 seconds with fully charged batteries, vs. about 5 seconds for the Sigma. The SB800 is probably overkill for your situation.