This whole domain thing is important. Lets get back to basics. Google is quite keen on Age Of Domain. If a domain has been around a while then it has a bit of a GRANDDADDY status and gets a tick in the box from the big G.
It wouldn't matter if a domain is KEYWORD loaded today. Let us consider your website a house.
When Standing on the ROOF you are at www.example.com here on the HOME page and with optimised Title Tags you are shouting out to the world what your website is about. Now consider your Landing Pages - you have brought your audience down into your house from the roof. Your House has many rooms each room a landing page so now we are are www.example.com/your-keyword-term-here.html now this landing page should be on topic and on theme about what your are talking about on the page. So if your 'on the page content' is about WIDGETS, then your Title Tag is focused on WIDGETS your page URL is at www.example.com/widgets.html

And if each page on your website was uniquely treated in this way by you , then you wouldn't need to go chasing buying loads of domain names that have keywords in them. You would have to spend all your time going around promoting them all after you have them 301 permanent redirecting into areas of your site.

Look at it this way. The BBC don't have loads of domain names. CNN don't have loads of different domain names, Walmart don't have loads of different domain names. What are - one site - one topic but with many landing pages. You want to find out about radio1 at the bbc. You go to www.bbc.co.uk/radio1 you want to find out about a presenter at radio 1 you go to www.bbc.co.uk/radio1/presenter
Why does google like the bbc site, cause its one site, google likes big sites that grow at a regular pace with new poages coming on at regular intervals. And, all the page content on this site is unique and each section of the site is on theme and on topic.

Forget about extra domains - get some decent URL addresses applied to your site and good anchor text links going from page to page that are relevant and you will in the long run have a much better site that will over time achieve the rankings you crave for.

There is no fast track secret way to have google do better with your site.

Hope this helps