Sounds like you came over from Eloqua!
The best way to do this may be a set of reports or smart lists. Unfortunately, Marketo isn't going to let you do exactly what you want.
1. Create a Smart List that filters Leads by Territory you want, then includes Leads who Clicked, Opened, Visited Web Page, etc. You can use the ANY or AND (ALL) criteria to decide if you want people who did any of the above, or just some items.
This will give you a list of Leads to further investigate.
2. You can use the Company Web Activity and Web Page Activity reports by territory to see which firms or leads are active on the site.
3. An Email Link Performance report will show you actively clicked links and then you can use that to inform #1 above.
4. Lead Reports- you could also use the Smart List section to constrain the report to leads in that territory by other activity and it will show you the resulting counts and let you drill deeper to see the list of leads. I prefer #1 instead though.