You have pretty much done your homework, 50mm f/1.4 and 17-50 f/2.8 makes a good combination for indoor usage, one giving you better range for group shots, and another better portraits with shallow DOF and neither one breaking your bank balance! However, for portraits, instead of the 50mm you could try a 85mm f/1.8 (price range almost same) which is a very good lens for doing portraits as well. As you already have the 50mm f/2.8 range covered with your zoom lens, 85mm f/1.8 makes better sense than 50mm f/1.4. Only problem will be sometimes you wont have enough room to use a lens this long, which could potentially be a problem for the 500mm as well. You can always buy the nifty-fifty (50mm f/1.8, ~100$) if you miss the 50mm f/1.4 setup too much!

Do not underestimate your kit lens. Its very versatile (f.e 18-55 can be used for descent macro works i.e butterflies, flowers etc). I always encourage beginners to get the kit as their first lens instead of buying something expensive because, using the kit helps you understand your shooting preferences, subjects, preferred focal length and thus gives you an idea of what should be your next purchase.

17-85mm does not differ too much from 18-55 in terms of image quality as opposed to 17-55mm IS or 15-85mm IS which are really good lenses.

EDIT: If you're decided on buying one lens, I'd prefer the Tamron 17-50 f/2.8 (currently on rebate in B&H) just because it'll allow you to take group shots as well as decent portraits. You can also consider the 50mm f/1.8, its pretty cheap and has amazing image quality as well as low light capability. You can get both of them in around 500$ now. Even if you upgrade to 15-85mm later and decide on selling off the Tamron 17-50mm, I'm sure you'll be more than willing to keep the 50mm with you.