How many pages/articles for a high competition keyword site?

Hello.
I just purchased an exact keyword domain.
It is a physical product and the keyword gets 450K without quotes and 246K searches with quotes a month at Google. Obviously, the niche is very competitive.
Now what I request you guys to suggest about is whether I should treat it like a Micro Niche and build 4/5 pages site/blog or should I make it a bigger/authority site with 50+ posts.
One more thing, no exact keyword TLD is in competition.

Really looking forward to your suggestions before I start off with this project.
Regards...

It mostly depends upon the quality of the post and Onsite/offsite SEO , If you have a domainname as keyword which you try to rank for , you changes of getting to first page of google is high , but not 100% certain.There are various factors which comes into play..like domain age of your competition and number of links they have , and number of pages index by google to a certain extent....i have been experimenting with this kindda thing , but no one knows how exactly google works.

But with the same name as keyword...You will get more preference by google thats certain.
I suggest 3-4 articles a month...and consistent whitehat link building should work for you....will be whitehat..and long term...

Thanks nixnash for your reply.
I want to add a thing here.
Although the competition is high, but the sites ranking on first page are amazon, official product page, youtube video, forum post and on page-2, squidoo etc. The highest number of backlinks on page-1 is 475 and lowest is 0 with PR n/a.
So what I think is that SERPs competition is not that tough.
As far as content is concerned, for another keyword which gets 90K searches a month, two exact keyword domains are ranking on first page of G, one of which is Parked :s and other has only one article on it and both have NO backlink at all.

What you say nixnash?

So far my site is concerned, for the first month, I am planning on to write 5 articles/pages for a test with high quality and original content and to build around 500 targeted backlinks. I think I am good at SEO both onpage and offpage.