To answer your last question first, Google says they treat all domain
extensions the same.
While they do, people don't. .com is usually the first choice when
typing in an URL.
I would go with a trial. Get your keyword rich domain and build a
store.
Here you have 2 choices.
You can have both stores use the same database or separate them.
Separation means more work, combined might mean duplicate content.
First, I would do the SEO work as this will show you what HAS to be
done to get top listings.
The domain name alone will not put you at the top.
SEO has consistently shown to have the highest ROI of any marketing
plan.
If you are going to go with the multiple sites plan, pick niches and
get the primary keywords in the domain name.
Forget "COOL" Think relevance to what you are selling".
As for the traffic, you need to think conversions rather than amount.
While deflecting traffic from your main site, a niche site would carry
more impact, and have higher conversions than a site that covers a
multitude of products.
Easier to get top SERPs also.
If you wish to discuss this further, please contact me in Instant
Messenger. (No obligation)
My IM contact information is on
http://nbs-seo.com/seo/contact_us.php
On Jul 19, 12:59 am, Luis Esteban Valencia Muñoz.