I have been using Blend Commerce for a few years now. Initially they performed the new site build on Shopify and have been upgrading and performing maintenance. Blend have been by far the best web development agency i've used (out of 5-6 others). What i like best about Blend is that they go above any beyond just doing the job. They send ideas my way, how things can be improved, best practices and things that have worked well with other clients. Highly recommended!