Hello,
I see that you are looking for a proficient Joomla developer for your website updgrade project, I can assist you with this having more than 12 years of experience working in Joomla, mambo, WordPress, Magento and Drupal.
I have worked with a client in Ontario for over 3 years on his several Joomla projects which included Template customization, Custom component, Module and Plugin development as well as creating custom Joomla templates from PSD based on Joomlart's T3 framework with complete responsive layout as per Google's standard.
I have been the Lead Developer for Humane Society of Canada which again was developed using Joomla as base CMS.
Please let me know if you have any customization done on your core Joomla or Vituemart files because that needs to be taken care of while the upgrade is performed such that the custom functionality is not lost.
Also if possible please share the URL of your Website.
If needed we can get on a quick call to discuss the above in detail,
Looking forward to hear from you and working with you,
Best Regards,
Garry