That 18-55 has the same specs as the lush Canon 18-55 kit lens, so I can't imagine it is going to be
that great.
The 55-200 f4-5.6 doesn't have awful specs, but I used a Sigma 70-300 f4-5.6 for a while and found it to be VERY slow at 70 (f4). Covering large ranges like that can make for increased distortion too, although if you read up on it you can get an idea of how it performs.
If you are looking for a great all-around lens, take a look at the
Tamron 28-75 f2.8 XR Di for a *mere* (depending) $360 with rebates currently
I just picked one up for my Canon and I love it, especially for the performance relative its pricepoint. It isn't quite as fast as the Canon 24-70 f2.8L I let go of, but considering it is less than 1/3 the price, I can live with *close* performance.
Read around
Fred Miranda in their Reviews section on a few of the items you are looking for. The site posts a brief synopsis at the top followed by actual user reviews which can be helpful.
I would assume the SB-600 is a solid performer, just not as strong as the SB-800. I wouldn't hesitate to get that....I just picked up a flash too and love it