I am starting a new site and I am wondering whether to go with 1-column page or shall I include a sidebar??

My home page will target a problem and sell a product that solves the problem. I will be targeting Search traffic and my site(wordpress based) would be a medium site, with 100 pages/posts. Except for the home page, most of my pages will be informative and the sales pitch will be minimal.

I want the site to look professional and nice but at the same time should have a good conversion. I know conv, depends on the content but for the sake of this discussion, lets assume that I have a good sales copy.

2-col: Most people have come across more 2-col sites than 1-col. So a 2-col design might be visually acceptable to them. Also, it makes the site look good and professional with proper navigation.
But there will be links on the sidebar to other pages of my site which, as I said before, will have less pitching. Now this might rob me some of my conversions.

1-col: I believe 1-col gives an impression that site is thin, probably spammy. And it doesn't looks not as professional as a 2-col site. But since there are no links to divert the visitor to other pages of my site, it might be possible that conversion will increase.

Whats ur take?

PS: when I say that 1-col site don't look professional, I don't mean portfolios etc. I am pointing toward content sites. I have never come across a 1-col content site that looks half as decent as a 2-col site.