Identifying a new lead in an existing account and assigning to a MKTO lead owner

Hello - we often want to send communications out from our Sales Owners to make them a little more personalised than our HTML marketing emails. 

How can we identify when a new lead comes in, but is from an existing client account? And then, from there, how can we then assign them an Owner (so that we can then send future comms from them), without pushing to Salesforce? Because at this moment, they are just leads which we wouldn't necessarily want to have sales follow up with yet.

Should we create fields for a 'Marketo Sales Owner', and have rules which would assign that based on their company name/domain? Then when they are pushed to Salesforce, we can update the 'Marketo Sales Owner' to reflect the actual Sales Owner?