Ecommerce Theme or Ecommerce Plugin

I am a webdesigner looking to code my first ecommerce WP site. Just some questions what you recommend…

Should I purchase an ecommerce theme and use the plugins, shopping cart, etc. provided? I am not finding any themes I really love?

Should I purchase a regular theme and then implement an ecommerce plugin with a shopping cart? How hard is that? Does this really work?

Can anyone tell me the pros and cons of either?

Also this is for an art gallery so they want it looking very high end and more of a gallery to purchase from then a shopping cart site, so the ecommerce themes are not looking like the best fit…can anyone recommend a theme?

Thanks!!!