Hi - I came across this and thought it might be worth mentioning another option, particularly with 10,000+ stock lines.
Full disclosure, I'm with Tall Emu. We're Australian business software that integrates with MYOB, but handles much more of the operational side - inventory, purchasing, sales orders, CRM, warehouse, freight etc.
We work with wholesalers and distributors that want to keep MYOB for the accounting side, but have reached the point where managing a large product catalogue and the processes around it in MYOB is getting difficult.
I also noticed your comment about having another program sitting between MYOB and your website. That's something we'd be happy to have a look at too. We do custom development and integrations where required, so you're not necessarily limited to what the software does out of the box.
I'm obviously biased, but with 10,000+ stock lines it might be worth having a look at Tall Emu before putting too much work into trying to make the existing setup do more.
Happy to answer any questions if it's of interest.
Rachel
Tall Emu