I'm on Mac and did my site in Adobe GoLive with has been discontinued and now it's all Dreamweaver.

You don't need any knowledge at all about HTML to do a site in Dreamweaver. They have templates too. You buy a book or two and plunge in. Most of them show you how to build your first site and walk you through it. There will be some swearing! You did say "powerful enough for a sophisticated professional site' and this is the program. You can probably do one in Microsoft too but I don't know if that will give you all you intend to need. All of these web site building programs are a little frustrating at first but with a popular one like Dreamweaver, there's loads of support sites and many books.

The days of having to know HTML to do a site was over many years ago. Good luck.

Once last thing: once you have a site done, you can open any web page up in any web designing program and work on it and re save it in that program because the underlying language is HTML.