Hi Malcolm, your main competitors on Google are as follows
www.diamondsisforever.com
http://engagementrings.goldenmine.com
www.bluenile.com
www.bestgem.com
www.theknot.com
Your site is great, megadescription add 'Engagement Rings' 'Rings'
Look at your competitors sites, check their keywords, follow their liks by typing "theirsite" into a google search box, follow their links and put your site in as well. Drop your opening megatag of ampalian and go for 'Engagement rings from Ampalian'
Then really hit those Directories. Good luck