Strategy for dealing with keyword variants

[PillarMarketing]

I'd like your opinion on the strategy of dealing with key phrase variants:

I've got a page that is ranking in the top 10 and top 3 for about 10 different variations of the same phrase.  Seomoz gives it terrible grades for all but one of the keyphrases.

Which course of action do you recommend :

----------- create new pages ------------

Create new pages for each variant and get them to grade A.

If I go this route what sort of cross linking scheme should I use between this pages?

---------- improve existing page -----------

Try to make my single page rank better for all the phrases by doing extra on-page work so the page has a better grade for all of the variants?

Many thanks for your ideas and opinions.

[OptimizeSmart]

Your aim should be high search engine rankings and conversions, not grades. Please bear in mind that seomoz grading system just promote seo best practices they don't have 1 to 1 correlation with search rankings. So i will suggest you to focus on link building instead.

[PillarMarketing]

Thanks for the reply. Anyone else have an opinion? Many thanks