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If your websites link extensively to each other thus forming a "Private SEO Linking Network", then yes, having it all together on one Server or Data Center is a bad thing.

However, just because each website has its own hosting plan with Go Daddy doesn't mean that they are on different Servers or Data Centers. Odds are, they are all probably in the same Data Center anyway (physically located in the same place).

Chances are, moving to an "Ultimate Hosting Plan" will not result in any changes to your websites; it will just be an "Accounting" change.

Duplicate Meta Description Tags are not a factor in search engine rankings.

The main purpose of Meta Description Tags is to be used as a sales pitch with a call-to-action to entice the user to click on your search result. There's no reason why you can't be a bit creative and vary your sales pitch a bit.

What you are describing is not a shopping cart website; it sounds more like a "classified" website. Maybe the WP plugin below is suitable? I haven't tried it myself by it seems to have all the features that you need.

http://wordpress.org/plugins/another-wordpress-classifieds-plugin/

Your Home Page is http://www.bannerbuzz.com/ while your Reviews are on http://reviews.bannerbuzz.com/review/18/Vinyl-Banners.

The first problem is that your Home Page is on the "www" subdomain while your Review Page is on the "reviews" subdomain. Subdomains are treated as separate websites by Google and so they are basically competing against each other for the same keywords.

I recommend moving your reviews to a sub-directory under the www subdomain so that your Reviews will have the URL like the following: http://www.bannerbuzz.com/reviews/18/Vinyl-Banners/

Your Review page has a lot more Text content than your Home Page. If you want to boost the rankings for your Home Page, make sure to increase its Text content.

Also, since you sell different types of banners, I reckon the Home Page shouldn't be the Landing Page for "vinyl banners". You should use one of your Vinyl Banner Category Pages instead:

http://www.bannerbuzz.com/custom-vinyl-banners.html