want a site of 20 pages with quality designs

That would depend on who does the work, and how you want it coded I'm sure. I would suggest you go to http://www.the-pixel.com Lindi is great to work with and does all my site work.

which country are you located in?

I guess that would depend on your skill level and what your looking for. there are many companies to choice from. I would suggest yahoo based it's pretty simple and changing information the store editor is not that difficult. 1 choice 4 your store, all web promotion are some good designers.