Best link building services?

Hey guys,

I'm new here, so a big hello!

I'm looking to build links to one of my sites. The site in question doing really well, with 2 million members and great traffic. Though I'm nowhere near the biggest in my niche. Obviously I don't want to risk damaging the website using dodgy services.

I've always been really cautious about buying links. And it's ultimately held me back. I know my competitors are buying links and always have done. It's not harmed them one bit, two of them are top 500 sites in Alexa. So the competition is steep.

When I first started this site, I built links manually, contacting bloggers etc and I soon burned out and become sick of it. For the past two years, I've not actively built links and focused on developing the site. Now the site looks great and works brilliantly but traffic has remained pretty constant.

Though if I'm going to become number 1 in my niche, I need to begin investing in some services. But which ones? there are so many that make big bold claims and I'm a little overwhelmed.

I want to maintain my natural link profile. Links from blogs (posts, sidebars, footers), blog comments, directories, forums and of course be able to alternate my link text and target urls and do so at a steady rate.

Any suggestions would be greatly appreciated. I'm open to investing in to more than one service, actually I'm guessing I'll need several to ensure the link profile appears natural.