What price range should I be looking at for a 15" or 17" screen?

15" LCD monitors aren't worth it. They are about the same price of a 17" LCD monitor. Unless you are really, really desperate to save $5 - $10.

17" LCD monitors ranges between $170 - $600 at Newegg.com. A large number of them are in the $170 - $225 range.

17" LCD monitors

However, you can also find a decent number of 19" LCD monitors ranges between $170 - $225 as well.

19" LCD monitors

Don't just simply buy the cheapest one because the viewing angles on some of these things are horrible (based on listed specs). You want at least 160 degrees viewing angle. Viewing angles can be as high as 178 degrees, but those are reserved for more expensive LCD panel technology and you will not find one in this price range.

For a 19" monitor I would recommend the BenQ G900 for $220 purely based on specs.

http://www.newegg.com/Product/Product.aspx?Item=N82E16824014155

Or the LG L1953TX-BF for $210, again purely on specs.

http://www.newegg.com/Product/Product.aspx?Item=N82E16824005095

In the 17" category I would probably recommend the Acer AL1717Fbd for $175.

http://www.newegg.com/Product/Product.aspx?Item=N82E16824009110

They all have the regular analogy connection found on CRT monitors (D-sub), and digital DVI as well. I would pick one of the 19" LCD monitors because the extra 2" for $35 - $45 makes things easier to read and of course looks bigger too. Go to a store and compare 17" (if they have 'em) and 19" LCD monitors to see the difference in size.