How would you Approach a Big Niche- One Site or several Sub Niche Sites ??

Okay, just having a little problem in getting a new Niche esatblished. I wont give the Niche away but I will use an example.

Say if I want to pursue the Home Furnishing Niche. And want to concentrate with a few affiliate Proucts but mostly center it around Adsense Earnings with Blogger Blogs.

Would it be best to have it all on one Site ?? Or have a separate sub niche site for each type of furnishing. In other wards a Blog for Chairs, another Blog for Beds, and another one for Shelves etc..etc.. ??

It just seems like the Adsense Ads would be more targetted towards each type of furnishing if they have their own Site. And thus get a higher CTR and CPC and avoid smart pricing.

And also instead of just one Domain name wouldn't it be more effective SEO wise to have multiple domains with each of the keywords used at each sub niche site. Example like fancyoakchairsdotcom and cushyoakbedsdotcom.
Rather than just one Site with one Domain like oakhomefurnishingsdotcom ??

What do you think ??

Thanks

Discrat